Atomic Clock thingy

[shabaviz55]

I think I'm a complete idiot for having this problem, but here goes. I'm using pawclock, because I like it , but every now and then, when I wake up, the computer's time is 10 or so minutes fast, and I think pawclock is too. What could be doing this? I re-synched it this morning, which works, and within minutes it was a couple of seconds off, which seemed really odd. Is it just me, or has it happened to others?

I leave the computer on 24/7, by the way.