This is just a stretch but is it possible it's not actually the launcher causing the problem but actually the version of Internet Explorer you're using? (specifically, it's out of date or corrupted?) The launcher client actually uses IE as it's 'base' so to speak, so if anything goes wrong with the launcher, it's usually IE acting recalcitrant (such as the version of IE you have on your system being out of date.). Internet Explorer 8.0.6 is the bare minimum version of IE required for the launcher to work, but SE recommends the latest version.

Otherwise the only other thing I can think of is to reinstall the game again and see if that helps (reinstalling will force the launcher to update itself).