As far as "Grease" goes, if there were some on the actual potentiometers, they should be conductive though I doubt any grease is necessary on a pot.
I also know that you can set the knob acceleration to "None" "Medium" "Fast" or "1:1" - You can try different settings to see if it works or not. Mine is set to "Fast" though you might try "Medium."
Another problem could be the computer itself. If your system is too slow, it could miss some of the midi data and jump around. A multiprocessor or multicore chip is ideal (Mine is a 4 core 3.4 Ghz AMD Phenom II X4 965 processor and an Asus M5A97 motherboard, 4 gig ram (dual 2 gig as dual channel architecture)
If the system is too slow, it can be a problem. Another factor might be the USB port and also interrupt handling (more detailed technical problem) which might have to do with other software running in the background causing interference with the MIDI signals.
Try a different computer, especially one with minimal software installed.