Disable Rule which is causing a redirect loop
You got a few options.


You can try to edit the data by deserializing it with PHP and try to get some meaning out of it. Most likely there is a status which is either 1 or 0.
You could delete the rule from the database entirely.
You can temporarily modify the rules_invoke_event (rules.module line 249 for 1.4), if you comment out the call_user_func_array call, no rule should be invoked on the site.


Either of these should work, personally I would go for the last one if I had write access to the rules files.