Hi - had same problem on Macbook. Solved it by removing battery, cleaning the edge all around battery (with sharp knife) and Macbook so it sat cleanly and its now fine.
Think the battery/debris was pushing on the underside of the trackpad/buttons which you can see when the battery is removed.
For my case, I concluded the trackpad issue due to the battery. Upon close examination, I noticed the battery was bloated (mine have been running since end of Y2008 without any battery replacement) and I have problem to put the battery back. I can fell the obvious clicking (sound/touch) differences once I remove the battery, the trackpad just work perfectly.
If your Macbook battery is removable and is located directly under your touchpad a bloated swollen battery could be the problem. Try this:
- Remove battery
- Connect to magsafe power and boot up.
- Try using your touchpad
If this fixes the problem you likely have a swollen or bloated lithium battery which can be dangerous. My symptoms on my 15" late 2008 Macbook Pro were that the touchpad acted like it was stuck in drag mode. The bottom left and right touchpad switches would not click or took great effort to press. I had to hit the touchpad very hard for a mouse click to be recognized. It also screwed up opration of my bluetooth mouse. I noticed several months earlier the battery cover no longer closed tightly; there was a gap. I should have been more curious as to why.
MacBook Pro (15-inch, Late 2008) MacBookPro5,1
FB4700LL/A ( MB4700LL/A )
"Battery bloat or “swollen batteries” is a common occurrence among older lithium ion batteries. It is commonly caused by overcharging a battery and then leaving it unused for a long time. It may also be caused by extreme changes in temperature. More often than not, battery bloat essentially “kills” the battery, rendering it unusable or unsafe for further use."