It looks like the extensions have caught up with Firefox 1.0PR. When I re-installed 1.0PR and tried to download the extensions that I have come to consider as indispensable (Adblock [*], DictionarySearch, GMail Notifier and Firesomething [OK, I admit, this one is more of a humour thing]), I found that these extensions happily admitted to supporting 1.0PR and installed without any problems.

All is well in the kingdom and the subjects are happy.

[*] IMHO, this extension is the single biggest differentiator between Firefox and Opera (along with Opera's inability to support Gmail).