So I came back to Skyrim, started a new playthrough (Female Breton Mage), finished Helgen, cleared Halted Stream Camp, cleared Bleak Falls Barrow, bought Breezehome in Whiterun and a couple of upgrades, killed Mirmulnir, became Thane of Whiterun, cleared Silent Moons Camp and Redoran's Retreat (for a Bounty), finished buying upgrades for Breezehome, then it happened... Trying to buy the Alchemy Lab, Proventus Avenicci takes my 500 Gold, the option to buy the Alchemy Lab remains in the list and no Alchemy Lab is added to Breezehome.

I bought it, went back to my house to check then bought it again THREE TIMES. I do have earlier saves but that isn't an option given the 3 or 4 hours I'd lose because of it and there's no proof that it will even work. Any other suggestions for workarounds would be appreciated.

everyone has same problem after installing dawnguard. only way to fix i know of is to uninstall dawnguard buy alc lab and reinstall