I don't believe this is a problem with this hack.

It looks like the issue on your board has to do with the dates for polls being stored incorrectly. This hack only formats the existing dates in the system so that they turn into "Today" or "Yesterday".
I have no idea what could be causing your particular problem, but I'd suggest that you take a look at any hacks you have that have anything to do with polls or new threads.
Also, another tip: Since you haven't yet upgraded to 2.2.6, when you do, install your hacks one at a time, and see if the problem persists. Of course, your dates will still be messed up (because they've been stored incorrectly), but you can test it out on a fresh test board, or in a private testing forum that you can set up.
Hope that helps.