I cant Log into Admin Area?!!

Hello all!

Had a zencart site up and operational for a longtime now, returned to the office today to spend some time updating our products in the catalog - and I cannot log in?

Ive entered my usual link to my admin area - https:
Ive entered my login details as I have for the past few months.
I can access my admin area 'home' page, as soon as I try and click any heading, customer info, order info - anything - it just reverts me back to the login page. This continues in a never ending spiral and as a result I cant modify the site, gain customer order info and print invoices, packing slips etc

Ive worked through the thread discussing:
"I can't stay logged in to my Admin"

It just seems strange that all of a sudden the site is now doing this?!

Any help or guidance would be greatly appreciated.

Many Thanks All

you're not alone, i keep getting this
0 DB_ERROR_NOT_CONNECTED
in:
[select * from project_version WHERE project_version_key = 'Zen-Cart Database' ]
If you were entering information, press the BACK button in your browser and re-check the information you had entered to be sure you left no blank fields.

Nothing has been changed but this is what i get when i try to go into my admin.
~Draven

If you have (honestly) done NOTHING to your sites - particularly configuration - then you need to have a quiet word with your host, who may have "adjusted" things on the server...