Running Fast Dial Version 1.x (most probably 1.90) one can encounter the following error message:

And in the error console:

This can all seem rather ominous.

However the cause is usually quite a simple matter.

In Fast Dial 1.x one is offered in both these menus a scaling option called Userlogos.org

or

Well unfortunately Userlogos is no longer available as a scaling method, and as a result of this there is an error message.

So all you need to do to remedy this problem is to change the scaling method in the Preferences Menu to either Default (works fine)

or Java

and then click OK, and the problem should go away.
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Regarding Userlogos.org as a scaling option:
This feature is no longer working because it used to produce very high load on server and was turned off on hosters request.
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It was drawn attention to on Page 34 of the Mozillazine site that there was a small bug in Fast Dial 1.90.

If the Toolbar button is Mouse centre clicked Fast Dial 1.90 will not open in a New Tab in FF 3.

This was confirmed by Telega

This problem only seems to effect Version FD 1.90 when used in FF 3.

With Fast Dial Ver 1.90, In Firefox 2.x, Mouse centre click on the Fast Dial Toolbar Button opens Fast Dial in a new Tab just fine.