Update: [TZO-27-2009] Firefox Denial of Service (Keygen)
Unfortunately the Denial of Service condition has not been fixed
with the new versions/builds and according to tickets filled
under the bugzilla ID the impact of this bug has changed since
version 3.5. 
Hence the list of affected products now is :
- All versions below Firefox 3.5
--- Comment #28 from PBForeman <firstname.lastname@example.org> 2009-07-08 09:14:00 PDT ---
When FF3.5 is open, cpu eventually runs 99%, using over 100,000K of memory.
Closing FF does not stop the cpu or memory usage. Closing with Task Manager is
the only way to exit FF. Previous versions of FF all ran stable, problem
started with 3.5. Closing and restarting does not solve the problem. Removing
program and reinstalling clean does not solve anything. Same settings were used
from previous version to install FF3.5. Once cpu maxes out, FF ties up entire computer.