Recurring Error In Logs
Design and Skin Customization
This means that that template has become corrupted on your file system - log in via FTP and delete everything in:
data/cache/jrCore
data/cache/XXActiveSkin
where "XXActiveSkin" is your active skin directory.
The reason this can happen even with you not doing anything is that every time your cache "expires", Jamroom rebuilds that cache from the templates - so if during a cache rebuild your server screws up in some way, or the file system has a "hiccup" then you can get a corrupt template.
Jamroom actually has several steps it takes to fix this first without bothering you, but if you see this in your activity log it means the fixes did not work - you'll need to manually delete the bad cache file.