A very common login problem looks like this:
You try to login onto machine chase from an xterminal, an Sun workstation or an xterminal emulation (on a PC). 
You type in your user name and password. The screen goes blanck or black and after a while the login prompt reappears.

This problem mostly occurs because the user has exceeded his/her disk quota.

The only way to solve the problem is to ssh into machine chase (eg. from 
a PC in 001). 

Then run the command 'quota -v' which will show you how many disk space you 
are using (1st number) and what the normal limit is (2nd number). You have 
to delete that many files such that you use less disk space than your limit is.
If you don't want to delete files move them to /hold/your_username.

Once 'quota -v' show that your usage is lower than your limit you can most 
likely login into your account from an xterminal.