Fatal error: Call to undefined function rules_events_global_user_argument()

Hello,

I have having the same problem as this person, but under slightly different circumstances. I am running Drupal 6.28 and when I activate the Rules 6.x-1.5 module, I get the following error:

Fatal error: Call to undefined function rules_events_global_user_argument() in /sites/all/modules/rules/rules/modules/comment.rules.inc on line 74

It is strange because I have several other instances of Drupal 6.28 running and there has been no issue with Rules on those sites. I can see the “undefined function” in the rules code, so it appears that Drupal isn’t loading the proper file (user.rules.inc ) for some reason…

So far, here is what I’ve tried:
- Deactivate all non-core modules and activate only Rules
- Make sure the webserver has proper permissions on Rules folders
- Tried the dev version of Rules

Any suggestions on what else I should try?

Thank you