So I've collected all pieces of the Mehrunes razor and turn them in to Silius, who proceeded on his way to Mehrunes Dagon shrine. I could keep up with him until about 300ft away from the shrine, when the game crashed, just before that bear at the bottom of the final stairway. I tried doing and alternate way, CTD; COC'd to mehrunes shrine, ending up inside no problem, then used unlock to head outside, CTD. Is someone else having this issue after the latest patch? And is there any workaround available atm?

Specs:

AMD Phenom II x6 1075T 3.00 GHz
4 GB RAM
Windows 7 64bits
Geforce GTX 460

Skyrim version: 1.4.21 (Patch from 1/30/2012)

Edit: ok, so I loaded a previous save, yet to recover the pummel, and tried to COC mehrunesdagonshrine, unlocked the iron gate to exit the shrine then, CTD... I just can't access the area on my current save. Is there any hope on this or the save itself is broken with no solution?
The good news are that this is related to the main quest, since a previous save before killing the Whiterun draon rendered the mehrunes dagon quest to work properly, I could access the shrine with no crash. But, after killing the hear the Greybeards summoning me, again the shrine is unreachable.

Hmmm, this is an odd CTD, especially when it is one spot but before the quest, as you mentioned, there was no CTD...

By chance, do you have any mods active?

Yes, by the time of the first crash I had several, tried disabling them all... no success, then loaded a save before the Greybears summoning as Ive mentioned on my edit post, then I could finish the Razor quest. Proceeded to disable the Deadly Dragons mod, and again after the summon, crash... I'm atm testing disabling the other mods that change leveled list and other stuff... will post results soon.

Edit: Now after disabling every mod I had active, again testing with an earlier save before the Greybeards summon, mehrunes dagon shrine working properly
Once the Greybeards call Dhovakin, then the access to the shrine is ruined.
So far, it's a bug related to the newest patch or one of the mods I had active wrote the save in a way unplayable. Or maybe something else, will check once the respawn period is hit...