If you are one of those who desperately wants (or needs) Wizz RSS to work on Firefox 5.0, please just reinstall 4.0.1.0, and it should work.
WARNING: I have done very superficial testing of 4.0.1.0 on Firefox 5.0 (I installed 5.0b7, but it updated itself, and now I have no idea what version I actually tested with, because Mozilla, in their infinite wisdom, only show 5.0 on the about Firefox page. Idiots!), and everything seems to work. If 4.0.1.0 breaks your Firefox, please don’t complain to me!
BUGS: If you find any, please let me know, so that I can try to fix them.
If you have already installed Wizz RSS 4.0.1.0, just reinstall it from here http://blat.co.za/XPIs/wizzrss4010.xpi
If you have “purchased” a nag free version of Wizz RSS, you can get the nag free version here http://www.wizzrss.com/dlnn.php
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Errrrmmmmm… Okay, I’m a bit slow. I didn’t realize the FF 5.0 final had been released today (21/06) – Sheepish grin. So when I installed 5.0b7, hopefully it actually updated itself to 5.0 final. My apologies to the Mozilla idiots for calling them idiots 
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