I was thinking this too, maybe for a different reason, but if you are using something, and it's sharp or rough[glass/rough stones/wood with splinters], maybe your Pacman accidentally cut itself crossing over?
I had to take out a rock from my frogs enclosure after I actually watched it roll over, just from them jumping on it, and was afraid it might squish or hurt them.
But GrifTheGreat pretty much said it all, a Vet sounds like what your frog may need.
Hope he/she gets better.