Known Existence: February 7, 2002
Pets are losing control flags unusually quickly at times. I have issued aggressive commands (attack and guard) and watched as only seconds later (as opposed to the 2 minute timer these commands are supposed to have), the pet turns blue. Of course, this is somewhat of an issue... unless you don't want the fame/karma or looting rights.
Solution: Keep close watch on your pet's flagging (easier to do for guilded tamers) and issue aggressive commands whenever control flagging is lost. Health bars in the 3D client do not properly update control flags.