I am having a somewhat different problem, but I think it is related. Using key words, adding, removing, changing is very slow on my Win XP SP2 system.
Using 3 ghz dual core, 4 gm ram, SATA 3G hard drive
I tried optimizing database, defragmenting hard drive which has 24 gb space open.
To delete one of two key words from a photo using LR2 stops the program for 25 seconds (before you can do anything with Lr). Doing anything with the keyword list takes the same 25 seconds. This includes creating new key words, deleting or moving key words, or adding a keyword to a photos.
When I open the same photo in LR 1.4, I deleted the same keyword (different database) and LR never slowed down. Response was instantaneous.
Both catalogs have the same number of photos and are large. (about 50,000 pictures)
Could this be the same problem?