Not sure how it happened but the main door has been renamed to "Bruma house test" and the main hall is pitch black. There are no lights at all.
The save i was using had 140+ hours gametime and i've been in and out of Frostcrag many times with no problems before this.

I used the "Quest award leveller v2.1.0" and saved my game inside Frostcrag.
When i reloaded and went outside (Only to forget something), turned around and door name had changed and on entry it was dark ?!!

Problem is all my saves are doing the same now, even my first save (20 mins into game).
I'm confused as to what this means.
Has anybody else had this problem !!!

I shall refer you to my lovely post on this exact same problem here. In short, I don't think there is a definite answer as to why this happens. I am curious, is this the 'Quest Award Leveler - Now Supports Battlehorn' (or something like that) mod? I wonder if that is a culprit, though it shouldn't be...

i've just read the Post, there doesnt seem to be a definate answer. what i do know is i used better frostcrag lightin before i formatted computer so it was probably still on my save, dont use it now
I now have frostcrag loading really late, no problems yet (touch wood).
Also for future reference forgot to mention that i used the tilde key (`) to change my hair style and saved inside FrostCrag, maybe because of that it happened, Wont be doing that again... Maybe thats a factor....

I can't offer a solution but I downloaded a mod for a "New Bruma House" which changes the standard in-game Bruma House for Sale, to an empty but gorgeous design more in keeping with the upper middle class houses around it. When I checked it in OMM it flagged it as conflicting with Frostcrag.

I like the Bruma house better than Frostcrag tbh. I'm thinking of getting a Frostcrag mod, because I really don't like the Frostcrag accommodations at all. It's probably one of my least favorite houses. (I've used Mod-replacements on all the in-game houses except Skingrad. Even Benirus Manor turned out really nicely after I switched to Benirus Manor Remade, and then disabled/deleted some things and re-furnished with a few items from Imperial Furniture.)

Just a suggestion, but I've had great success using FCOM Helper to load-order my mods. Sometimes a good load-order will help on conflicts. Not always, but I have read some threads where reversing the order solved mod conflict problems.