I have AMX and RealBot WIP installed just fine. But I get the same error when i have any bad modules installed. This is an extension to CybaWolf's list:

4.333333: If you get that error, disable any modules in your addons\amx\dlls folder.

4.666666: If that works, goto http://amxmod.net/forums/viewtopic.php?t=22409 and download all the new modules.

Hope this helps