we seem to have a similar problem, though, im not using the uberinstaller. try lyle's suggestion of "flushing" the imagecache presets. go to /admin/settings/imagecache and flush each preset. or you can try deleting all the presets and re-creating them by going to /admin/store and there should be a link there to create the imagecache presets. see if that helps.

i've been doing all of that since i reinstalled ubercart and it hasn't fixed itself yet. and my imagecache folder is erratic. sometimes it has the proper folders within it but not the files and sometimes it doesn't create anything inside it at all. anyway, i hope flushing the presets work for you. lemme know how it goes.