I had a similar trouble when I migrate my shop to 1.7
After investigation, I found that, -in my case-, it was probably cause by a problem during the salerule_setup upgrade process.
You should verify that you don’t have the website_id and customer_group_ids columns inside your salesrule/rule table.
If you still have this obsolete columns. You probably have like me a problem during this SQL upgrade :
* Create table \’salesrule/website\’ if not exists. This table will be used instead of
* column website_ids of main catalog rules table
* Create table \’salesrule/customer_group\’ if not exists. This table will be used instead of
* column customer_group_ids of main catalog rules table
* Eliminate obsolete columns
Simply remove website_ids and customer_group_ids columns of salesrule table was enough for me to fix the problem.
Hope this helps,