Sounds like they're not seated on the rims. I have the same problem with the rear-wheel of one of my bikes. It's caused by there being a rough spot on the inside of the rim, which the bead of the tyre has a problem moving up on to - the only way I've been able to cure this is to use a Q-tip to smear some liquid detergent (neat washing-up liquid) on to the bead at the point where it needs some help, and inflate to 125 psi. Works every time!
Hope this helps!
- Wil