I have been following all the complaints about the frame rate drop issue, and I must say I have never experienced this problem. What I have been experiencing is a much bigger issue than that! I can not use the barter system (buy/sell) at all, or complete any of the quests. The game has become unplayable. I went as far as to start a new game file, new character and everything, but it only started happening earlier in this (my second attempt) playthrough.

When I try to buy/sell something, the menu showing the items available never comes up so I can't make any transactions.

Also, whenever I try to do a quest, it gets stuck (actually just stops and wont let me continue past a certain point) so I can't complete it. Eg...
Won't let me insert the sword in Red Eagle's cave, so I can't fight him.
Won't let me past Sparing with what's his name in the companions quest. The sparing just keeps starting over.

My file size was about 6Mb when this started happening, so this is what led me to the frame rate topic since it was the only bug people were raging about, but lag isn't the issue. Does anyone else have similar problems, and does Bethesda even know about this? They should by now if they actually did any real product testing on there products. This IS a GAME BREAKING BUG that MUST BE FIXED!!!