Have the exact same problem. Skyrim didn't want to launch. And suddenly it started to download something (after Library, Right click Skyrim, Properties, Local Files, Verify = Everything OK). Now the download progress is on 1% (which it has been the last 10 minutes)... Crossing fingers that it will DL completely (and soon...)
Edit: It is not DL anything at the moment. It is Validating: 1% Anyone know what's up (completely new to Steam)
Edit 2: Have restarted the Library, Right click Skyrim, Properties, Local Files, Verify and there now seems to be some progress! And: All files successfully validated. And now! It DL's (probably the patch) and I am up to 15%...