[@netweb Keymaster 12 years, 12 months ago]

I’d suggest disabling all your other plugins to make sure there is no conflict:

To try and resolve conflicts with other plugins please disable all your plugins except bbPress to see if the error persists. Re-enable each plugin one at a time and if things break again you should be able to now know which other plugin is causing the conflict.

That said I think it is more likely a theme issue, what happens if when using Twenty Eleven/Twenty Twelve/Twenty Thirteen themes? Does the issue still persist?