PHP Script can't write to cache (fixed, but why?)

Odd occurrence, I just had two sites on one of my VM Pro servers where the site was down or malfunctioning which I discovered was because the cache directory (plus more) couldn't be written to. Looks like they suddenly needed Apache ownership. All my virtual servers use FCGId - I was able to fix by going into Website Options and re-saving as FCGId. What happened, was this some sort of bug?

I could have more sites effected, but it's a lot of sites to go through one by one. Anyway to globally re-save all virtual servers as FCGId?