I was getting this error when trying to extend SharePoint to another web application:
The Execute method of job definition Microsoft.SharePoint.Administration.SPWebApplicationProvisioningJobDefinition (ID 22631de2-0c21-4e1b-aa9c-12e4f60a18f6) threw an exception. More information is included below.
"SharePoint – eicomsp4:80" contains illegal character ‘:’.
Turns out that, somewhere along the way, SharePoint allowed a colon in the name of another extension that was now causing the timer job to fail. I also had to delete the "run once" timer job that was associated with the failed extension attempt. Weirdness.