Suddenly Getting a blank screen and no error messages after clicking to login

Getting a blank screen and no error messages after clicking to login. Url sticks on index.php?main_page=login&action=process - not on shipping. Just started happening 2 days ago. The first time I checked I found error messages about the USPS unsort and reinstalled USPS though no messages had happened before. I made sure I had the correct file and that error went away (was happening when trying to access the login page then). I turned on strict error reporting and nothing showed up.

My mind is blank - what could cause this and not leave any trail? and start abruptly?

Use FTP and sort by changed date and look for file alterations around the time this happened

check:

• configure.php changes
• SSL changes
• addons added/removed
• changes related to cookies
• is zenid cookie getting set, does domain match the store
• other browsers affected
• other computers affected
• php version change
• cpanel automatic updates to server config overnight

well, I never did figure out what was wrong but uploaded all default files again (there were 2 installations, a 1.5 and a 1.3.9h) and this was on godaddy. Seems to be working okay now. And yes, I told her keeping her sites on godaddy was not a good idea.