A bug of forum(apps)

Idk if I post this in a right section.
I just setup my forum, and I found a bug of board style. I installed a style called AcidTech, then switch my style to this in the user control panel, after this I can’t submit any form in my forum, UCP, ACP, posting/threading, system always tells me ‘The submitted form was invalid. Try submitting again.’

Then I delete my forum app and setup it again, installed and switched to AcidTech style, the same thing happened, so I guess that style is bugged.

I have not tried AcidTech Tiger style, but AcidTech is the only one with this bug I ever tried.

My browser is Firefox 3.5.3

A search on AcidTech bug suggests that you rename the folder to be all lower case, which is the convention for the default styles.