I hope I picked the right thread.
I used windows 7 64 bit and Photoshop CS5. I tried getting the 3.4.1 update through the autoupdater but even though it seemed to download the correct version, I got an error message that the version wasn't compatible. When I logged in here and did a manual download, everything went perfectly. I'm not sure where the bug is but I thought I'd report it.
Thanks again for Curvemeister, it's indispensable for me.