It seems that after downloading dawnguard i can't play skyrim anymore... I usually play with 10 mods or so but even if i disable them the games keeps crashing to the desktop from the main menu.. If i deselect dawnguard from the data file i can normally play. Anyone has my same problem?

Yes, I have exactly the same problem.

I haven't found a solution yet.

Where is Dawnguard.esm in your load order?

If it's at the bottom, try moving it to the very top.