I got this error while creating a new site collection , i was wondering what might have caused this issue. The last thing i was playing with was custom alerts and the error showed something is messed up with the timer schedule. I thought of checking the interval set for scheduled jobs and Volla!!! i had set the immediate job timer to "every 1 minute " which is not a correct string .
So solution is to reset the property :
I used the follwong command to set the timer :
stsadm -o setproperty -pn job-immediate-alerts -pv "Every 5 minutes between 0 and 59"
and all worked great :)