Hey BITTHT,
First
there are two condition fields in Magento: in the tab "Conditions" and in the tab "Action".
Check out wether both is empty.
Second
Check out if all caches are properly working. Usualy there should be a big yellow warning in your Admin-Panel if it is not so.
Third
If this does not help and you are advanced enough you could check out the "salesrule"-Table in your Magento SQL-Database.
(Important: make a Backup of the Database first!)
Just add from your Magento-Admin-Panel a new shopping cart price rule and check out wether it is working correctly.
Then go into you SQL-Database (for example using phpmyadmin (if installed)) go to the "salesrule" table and copy paste the entry of the collumns "conditions_serialized" and "actions_serialized" from the new price rule to the old one.
I hope I could help you
Christian