I keep getting these alerts every hour, what does it mean and how do i fix it?

The following number messages have been logged since Tue Aug 09 17:02:02 EDT 2011 :

       0 Fatal messages.
       299 Error messages.
       0 Warning messages.

The last few messages are:

[ERROR] Updating last contact time failed Assert failed: beginNestedTransaction in statement [UPDATE device SET last_contact = 1312927303993 WHERE device_id = 102898]

[ERROR] Updating last contact time failed Assert failed: beginNestedTransaction in statement [UPDATE device SET last_contact = 1312927319821 WHERE device_id = 39741845]

Thanks