Well, it's more like a new variation of an old problem.

Before, I was experiencing multiple problem vectors:
Bookmarks disappeared
FD wouldn't display titles
FD wouldn't place bookmarks where I drag&dropped them

Now, I only have a recurrence of the drag&drop issue, as a solo problem.

When I attempt to move a bookmark to a new tile location FD will ONLY place it in the position on the tile grid BELOW where I "drop" it. Before, the issue was solved within the preferences/sort menu. Before, there was no sort option showing as selected. As soon as I selected "none" as an option, my problems went away. Well, the drag&drop problem has returned. As near as I can tell, I did nothing to precipitate the revisit of the problem. The ONLY change I have made, today, to ANYTHING, was updating my Zone Alarm Firewall.

OS - Win Vista HB
Browser - Firefox
Add ons - XMarks(3.3.2), Fast Dial(2.23b1), FlagFox(3.3.16), FlashBlock(1.5.11.2), NoScript(1.9.9.01), and wootwatcher(1.0.6)
Any guesses as to how to fix this? So far, I have:
1) Gone in and selected a different sort option, and then re-selected "none." - This solves the problem for approximately 2-3 tile moves, then is goes back to putting them below where I drop them.
2) Done the above and shutdown/restarted FF, THEN re-selected "none." Exact same effect as above.
3) Shut down & re-started the box. - Solved teh problem for approximately 15-minutes, then, it returend to dropping tiles into the box below where I release them, again.
4) Closed my eyes and prayed for the mental strength to not put my fist through the screen - This seem to be working, so far, as I have not yet punched my computer in the throat. It still drops bookmarks into the tile below where I want them, but, as long as I do not want them in the upper most tile, I simply release them above where I actually want them and the go where they want to, which ends up being where I want them, anyway, as long as I want them one box below where I want them... Durh!!!

Mmmm...

I was waiting for you to say this....

I am experiencing a similar problem which I am trying to understand.
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Well, at least I am not alone, this time!!!
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1.
I found that if I went back to default settings and reset defaults, I was able to move cells around OK.
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I'll try this approach. It's better than nothing
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2. The moment I re-entered settings as they were before the problem resurfaced.

It is most frustrating.
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I share your pain, my friend. I share your pain.
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Apologies that my answer is not very helpful.
Please keep me posted if you discover anything.
Maybe we will solve this somehow !

Many thanks
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On the contrary, your answers give me a place to start
I'll post back any revelations I discover

Luck to us both!

Mmmmm.....

I guess we should look for common elements.

My grid is not large 3x10 3x12 that sort of thing.

I do not use your firewall.

I guess all we can do is exclude things and see if it makes any difference.

I have been playing around seeing if the mouse is at fault.
Tiresome...

I do not move cells around much, but when I do I like them to move to where I want them to.

My fear is that this is a corruption of bookmarks.
I have uninstalled and re-installed FD as well.

What is your Firefox Version ?

Many thanks

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I guess all we can do is exclude things and see if it makes any difference.
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My thought exactly

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I have been playing around seeing if the mouse is at fault.
Tiresome...
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I don't think it's the mouse, or else the problem would most likely present itself more often, I believe.

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I do not move cells around much, but when I do I like them to move to where I want them to.
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The only time I move stuff around is generally when I re-size my grid, like today. Which is why I thought that might be a key component of the malady.

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My fear is that this is a corruption of bookmarks.
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Crap! I hope that is not the case. I've got, like, a grillion of them. I keep meaning to take some time and go in and clean up my bookmarks folder(s), but I never do.
Could folder size be a component of the problem? How do I find out how large my bookmarks folder is?

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What is your Firefox Version ?
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I'm running 3.5.3, I think is the latest version.

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Many thanks
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Many Welcs, in return!

I just saw that. For me it is the opposite. I already had "fixed" deselected and selecting it seems to have, at least temporarily solved the problem. I say temporarily because, every time I think I have my *EUREKA* moment, it goes back to the same problem.

At this point I'm guessing buggy-code, and it's simply a matter of eliminating what is not the problem...