Yes, you are right. It is the flash plugin. The flash plugin is not open source, alas, and that is why it sucks. =) Macromedia wrote it for us linux users, which was nice, but it is not very good, but since they did write it, which is alot more effort than alot of other people for linux support, I appreciate it.
Just uninstall the flash plugin, unless, of course, you are addicted to flash movies.