Commerce - selecting attribute results in ajax error when product has many attributes I've got a commerce store running well on a Windows IIS server. The only problem is on certain products which contain many attributes (e.g. around 10 or more) the ajax doesn't work when an attribute is selected. The js error in the console is vague as ever:

An AJAX HTTP error occurred.
HTTP Result Code: 200
Debugging information follows.
Path: /system/ajax
StatusText: OK
ResponseText: 


There is nothing untoward in watchdog or in error logs. 

The fact that this happens on products with many attributes suggests some sort of PHP limit is being hit, but there are no errors to suggest this. Also worth noting that this is working fine on local/staging server so it's something server based that is the problem here.

Any ideas?
Experienced the same issue. Apache error log "PHP Warning:  Unknown: Input variables exceeded 1000. To increase the limit change max_input_vars in php.ini."

Editing php.ini and setting max_input_vars to a suitable figure fixes this.