CiviRule Error on Event as Linked Trigger
Thanks for reporting this CiviRulesbug, we appreciate it!

CiviRules, as you might know, has been developed by CiviCooP to suit the needs of some of our clients who meanly deal with fundraising. So the conditions and actions on Contributions are fairly well tested and stable.
Althought we developed CiviRules initially, it is a community extension and we do not feel we are the owners. We do not fix all issues with CiviRules, much like the CiviCRM core team does not fix all issues with CiviCRM. It is a community effort, of which we will take our part.

Based on this, would you be able to dive into this issue, debug it and solve it? The technical documentation on the wiki (http://wiki.civicrm.org/confluence/display/CRMDOC/CiviRules+-+how+to+make+your+own) should give you an idea how the engine works. I would start with testing the condition with other actions to find out if the problem is in the condition or in the action. As you already done part of this, it is probably best to start debugging in the condition and more specifically the isConditionValid function.

If not, would you have the funds to pay someone to fix the error? Or are you just reporting it and happy to wait for someone else with the expertise or funds to fix it?