Quantize errors

Howdy. I'm trying to sync MIDI events (notes) to an audio track. The grid is good, the tempo map is good, but when I try to quantize the MIDI notes to the grid they appear late and sound late. WTF? Help! Latest version, MACBook OS 10.6.1

New info 

This is an item that loops along, yes? If yes, the loop is slightly too long.

long shot but go into your midi items properties and make sure the offset is set to the same as the start of the object.

I think I figured it out. The tempo map changes throughout the song, right? When I add notes one at a time there's no problem. When I copy, say, a chorus, for example, and paste it at a location where the tempo is slightly different the pasted notes WILL NOT conform to the tempo map at that spot. Even if I force quantize. So I ended up writing all of the notes individually. I also found a workaround by importing the MIDI file into Logic and quantizing it there. Logic doesn't seem to feel obligated to honor the original tempo when quantizing. Odd.

Thanks for the tips, folks.

In media properties (for that item) is the "timebase" set to start,length, end (or whatever it is called)? it will automatically change if this is on for the item. You should also set this as your initial mode in the songs preferences.