EOS 60D - image file name problem

Hi all, quick question: I have a 60D, updated to firmware 1.1.1 (which is still current acc. to the Canon website).

Since the update, my image filenames are strange:

Instead of "IMG_0001.JPG"

it comes out: "_MG_0001.JPG"

It was not like this before the firmware update.

I've searched the menus through and through for a setting to change this, but cannot find anything. Has this happened to anyone else?

I can imagine trying to reinstall the current up-to-date firmware may be a solution, but I wanted to ask if anyone else has maybe had this problem/phenomenon before?

Thanks in advance!