NVFS brought changes to the Palm OS programming and not all applications reflected them. (Those that were last time updated prior to NVFS release, could not.) One of the most frequent problems is that the Palm databases are no longer fixed. That's exactly the problem that is targeted by Resco Locker. For more detailed explanation of the NVFS specifics see please the discussion on the Resco Backup product page.
As a side effect, applications locked in memory need less time to load, which in turn may increase the performance of your handheld.