Hi! i've just registered. I'm playing Morrowind with the two expansions and the overhaul.

But i've two problems:

1- Sometimes i encounter people who are surrounded by a yellow triangle with a "!" in the center. The game shows me an error and ask me if i want to continue. It's something with a texture load error.

2- Sometimes when i rest, at the awakening there's an assassin that want to kill me, and he's also surrounded but the yellow triangle. In this case the game shows me a lot of error, and i must to select 'yes'.

How can i solve? Thanks in advance for your help!

Looks like you installed the expansions in the wrong order.
They must be installed like this: Morrowind->Tribunal->Bloodmoon

You don't need to uninstall anything, just re-install Bloodmoon.

If you're on Windows7 or Vista, you should also install the game outside of Program Files.
There's info http://www.gamesas.com/topic/1305729-mod-recommendations-for-new-players/ on how to install Morrowind outside of Program Files, and for Steam users.