I have noticed that since Firefox 3.6.9, the add-on do not get installed. So I thought of disabling ZASS Toolbar. This basically kileld the functionality of the ZASS toolbar, but what was annoying was that I still could not install many of the Firefox add-on tools.
So I had to decide functionality of ZASS toolbar v/s add-ons.
I tried deleting and COMPLETELY removed Firefox from every nook and corner of hard drive and registry, and then re-install Firefox. It did not help. So the suspicion was on ZASS.
I then compeltely remover ZASS using ZASS remover tool; removing all registry enteries manually. Then I installed fresh copy of Firefox with add-ons I wanted (AdBlock Plus or NoScript). Then I re-installed ZASS. It worked. However, I could not update ABP. This indicates that all firefox add-ons are incompatible with ZASS toolbar.
Then one time I deleted "C:\Users\username\AppData\Local\Temp" folder and then I lost ZASS toolbar in firefox.
Not even re-installing Firefox worked. So I had to delete Firefox, remove its registries; delete ZASS, remove ZASS registries, then re-install Firefox and then install ZASS.
Thus it is very clear to me that the new ZASS does not sit well with updated Firefox.
So, if ZA develpers are listening/reading, could you make sure that the ZASS toolbar do not conflict with Firefox or IE toolbars? This problem is over a year old now for me.