Seams in QuickTime and Flash

Disclaimer: I'm a hobbyist with only the most rudimentary graphic editing skills.

Over much of the past year, I made QTVR panoramas with PTMac. My 6 horiztonal shots stitched wonderfully, but adding the zenith often caused errors with seams, in the triangle formed by the zenith shot and the first and last horizontal shots. Usually the error would be a small section off by 1-3 pixels. I'm working on acquiring the graphic editing skills to take care of such errors.

Not too long ago I bought PTGui and remade a few of my earlier PTMac panoramas. In some cases seam errors have disappeared or they have become harder to find because a bit of blurring at a seam makes a 1-pixel offset harder to see. After going through my optimization stages, I usually end up with a message informing me that my final optimization is very good. In all honesty, does PTGui offer a better evaluation, perhaps "excellent" or "panoramic Enlightenment achieved"?

I also have a copy of Pano2VR, although I haven't been using it much, because I need to improve other skills. However, I have converted a few of my remade PTGui panoramas to Flash 9 with the default settings and I have found seams that I can't see in the QTVR version but do appear in the Flash version. Why is this? Am I simply not looking close enough at the QTVR output and thus missing the flaws that show up in the Flash versions?