X2 on what zwiller said. Try un-installing LSP, then un-install the codecs, then re-boot. Then install LSP and select the default codecs, re-boot and then run LSP. I had a heck of a time with the codecs when I first upgraded to LSP 2.5, after I did the un-install of ALL the codecs, it speeded everything up.
I have a similar spec'ed machine to sirloinofbeef001 and mine is now running fine with the latest update.