its a logging feature found in the core.js, its a form of timout exception(but not really an error) its sent before logging any info.
For your situation its todo with somthing else! is your site going slow? have you created anything recently? you need to find the site its come from and then the page and delete it and recreate it and the message will disapear! you get this error after every missed 50 milliseconds i belive and this will run slowing down the site.
you should see below the error you posted another error detailing where its faulting! can you post that?
Based on my understanding is that its running into a deadlock! from the error you posted its refering to a stored procedure that is failing and its in a constant loop and then times out which inturn runs the timout function in core.js!
This issue was resolved within 2010 but looks like its back again in 2013 lol, this can occure from a stored procedure that is say ment to return an int value but instead returns null or could be from offending repeating urls where its listing (waiting) for one stored procedure on sql server that is in lock position and that same locked stored procedure is also waiting for that other stored procedure so you have a deadlock on a table that is not returning the correct results back causing timeouts!
there are two options! one is to update sharepoint 2013 using the hotfix april cu 2013:
note that its a hit miss with people!
you can run a script but it also has a mixed bag with the result being that it delets wanted navigation that you would need to out back together!
or the simple method of trying:
Navigate to the content and structure (Site settings > Manage content and structure)
delete the affected sub sites
restore them back from the site collection recycle bin (Deleted from end user recycle bin)
script can be found here with a detailed expo on the issue: