This usually means that you have exceeded your disk quota and your account has been "locked". Try doing either a command-line login, logging in on the Windows machines, or doing a remote login using ssh, etc. If you are able to log in any of these ways, try typing

showusage

to see if you have exceeded your disk quota. If this is the case, erase some files, return your account to below quota levels, and the problem should be solved. You may want to check your internet cache directories for large, unneccessary files that might be stored there. For more information on CIMS disk quotas, go here.