When I try to use the "Open With" context menu command to open a .jpg file with Paint Shop Pro Photo X2, Paint Shop Pro Photo X2 loads, but the picture doesn't open.
If I use Computer (Explorer), it works fine.
I am using Vista 32.
Are you selecting PSP from the Open With dialog directly, or using the Browse button?
Directly.
There might be something unusual about the way PSP has configured itself to launch from the Open With list. If you can help track down how it's being run then hopefully the problem can be fixed.
The first step is to open RegEdit.exe and go to
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts.jpg
(That's for the .jpg extension. If it was a different one that you had the problem with then change the .jpg part as appropriate.)
Could you go there and tell us what is below it? There should be sub-keys (which look like folders in RegEdit) called OpenWithList and/or OpenWithProgids; which values are inside of them?