Cannot add categories, or users – the button does nothing.

Hey everyone.

For the last hour I have been looking through threads trying to resolve my problem.

When I go to add a category, I enter all the information and click ADD. Basically the button is dead. I click it and NOTHING HAPPENS.
no refresh, no added category, no errors, nothing!

Its like the button is there just for show!

Same thing when I go to add users. Enter all the info, click ADD and NOTHING. I have tried this in IE, and Firefox. No luck!

I have tried to delete cookies – nothing
I have tried to create a .htaccess text file and upload it to wp-admin with this code

<IfModule mod_security.c>
SecFilterInheritance Off
</IfModule>

and it does not work!

Basically if I cannot add categories or users, wordpress begins to become useless. I know there is a way to fix this, but I am seriously stumped.

Please help me out, I really apreciate it.
-Matthew