I am running win7 64 bit with 12GB RAM and installed Lightroom 4.1 RC2. 1) I am (trying) to edit large panoramic files, and the 1:1 preview images do not seem to be saved from session to session. Images take quite a while to load in Library and even longer in Develop. 2) There seems to be a major memory leak. Upon startup I can edit a couple of panos, but then the machine becomes very slow and basically quits working. 3) I don't see "x64" in the tile bar. Is it running 64 bit?
Running Win7 64-bit here as well and installed LR 4.1 RC2 last week. There is definitely a memory leak of some sort, as I too am experiencing major latency after a few minutes of editing. When I check memory usage in Task Manager, I'm seeing more than 2GB (of 4GB) of RAM being consumed by LR and my machine is running like molasses.