If the portable install works & the other when updated to use the same version doesn't then it's most likely an odd config problem since the skin shouldn't matter especially if set to a classic one. Other than bundling up the broken installs main set of config files so I can have a look at them I'd rename the winamp.ini to something else & then run it again to see what that does (it'll reset most settings & window positions but is the simplest way to see if it's likely the main config file at fault).
