I have it installed to my 360, same as you I also did with Oblivion and FO3 just because of the amount of load times you would get without and glitches, etc. I have cleared the cache with no result, so I guess i'll have to wait for that next update.
Just remember that Fallout 3 had a lot of problems during launch, as well (though, hilariously enough, no reviewers seemed to mention it. I guess Bethesda's hands were deep in the pockets of the publications at that time.)
So, give it some time, and I'm sure you'll have a good experience. This game is superior to Fallout 3 in every way and more in line with Fallout 1 and 2.