Vista - Fallout 3 In-game error

Ok, here is the problem- the game starts normally, and perfectly.
But, when i go and start a new game, the dialog is really, really slow and when when i load a game, all the npc's neck will be twisted 90 degrees around, and when they are walking, the legs doesn't move. Anybody here experience same problem or got a solution for this? p.s i tried re-installing it a few times, the same CD works perfectly on my cousin's pc, which is XP SP3 Pro.
CPU spec:
Processor: Intel core 2 duo 2.26 (2.52 when overclocked, and i overclock whenever i play a game and they work perfectly.)
System: 32-bit Windows Vista Home Premium
RAM: 4GB
Graphic Card: nVidia GeForce 9800M GS
Manufacturer: ASUS
Thanks in advance

Hello sjb411,
Is the game patched up to the latest patch 1.7 ?, I will assume you have the latest video drivers, this game is great, but can be a bit of a git to get it to run right.

erm... no it's not updated YET, but im planning to update it on monday (since the update is in my hdd which i don't have right now)'
The drivers and directX is up to date, so as my specs. my specs wil be enough to run fallout 3 on high, i believe anyway thanks

There is not much you can do until you have the game patched to the latest patch, there were a lot of bugs in the first few patches so it's essential that the game is up to date.