Well, it's hard to say for sure since you don't say what kind of heli you have, but I'm going to guess it's FP, maybe a DF4.
Generally, I've found that when everything else checks out, it's a problem with the new blades. Try running them quite loose, and then quite tight, and let me know what happens BOTH ways. Also, did you balance them and set the tracking?
I've found that 99% of the time a wobble is problem with blades.