PSP analog nub fix

[Thorax]

I think I posted something 6 monthes ago about my nub being messed up. It would turn and move if I slightly bumped the nub and was constantly probalmatic. So last night I took out my nub and looked for anything broken. Nothing looked broken so I took it apart. Again nothing looked broken. I tried to remember what my post was about and what it said to do. So I searched my post and found it. All it said was to take my nub off of the faceplate then screw it back on. That didn't work. So when I was trying to get my nub back together, I noticed some gray grease stuff on the pcb. I wiped it away with a pencial eraser and finished puting my nub together. I started my PSP back up, went to the internet browser and moved the mouse around. It worked perfect. here is a video http://video.google.com/videoplay?docid=-7800258867175013512

[Dazzerr--]

I had a problem similar to this, what was the gray grease stuff. do you know?