I've been having the same problem, only slightly different... My initial game load takes around 5-10 mins to load, then it loads up fine. But it has the lag in game, so I would simply re load that save from in game and it loads in about 20 seconds and works nice and smooth. However, I am currently in Cidhner mine and every time I 'serve my sentence' the never ending loading screen appears.. It's incredibly frustrating as I've spent over 191 hours on this save (It's my only one). And I don't see any way around this as all of my auto saves are in Cidhner mine for some reason.. Any suggestions? I really don't want to be starting this all over again..
P.S. I would load an older save but I forgot to save for a while and it's literally 6 hours+ behind my auto saves.
Try clearing your cache, then download the patch again on start up. If that doesn't work, you will have to reload you your last save and it might suck going back 6 hours, but that is a heck of a lot better than losing 191 hours isn't it.
Also remember to save more frequently in future just in case this sort of thing happens. I myself have been in this situation, maybe not 6 hours back, but having to redo anything that you have just done makes it feel like a chore.
Bundy is as Bundy does