Delete key not working with Firefox and FilteredTextBoxExtender

I'm using FilteredTextBoxExtenders for my textboxes with filtertype set to numeric. Everything works fine in IE but in Firefox, the delete key and arrow keys will not work in the textbox. Backspace key does work. This is a problem if the user needs to change the contents of the textbox after somethng has been entered. Is this a bug, is there a fix?

I'm also having this problem, has anybody found a solution to it?

Thanks

Just wondering if a solution had been found, as I'm struggling with this too, and it's not too well documented on the web