An M20 pilot took off and almost immediately sank back toward the runway for unknown reasons; and was unable to get the landing gear back down before landing.

Narrative

Preflight was completed with no issues identified. I taxied to the ramp and fueled to full capacity; 64 gallons. I completed a final weather briefing using 'ADDS' and 'DUAT.' After reviewing preflight and completing start checklist; I taxied to Runway X for departure based on wind information; 200 degrees at 17 KTS gusting to 21 KTS. I completed a run-up and the Before Takeoff checklist. After a review of the takeoff checklist; I taxied onto the runway. Upon acceleration; I noticed a roughness in the ground roll and aborted the takeoff 1;000-1;500 FT down runway. Upon deceleration and taxi back to Runway X; I determined that it was just a rough spot in the runway surface. Before taxiing on Runway X; I made a quick review of before takeoff and takeoff checklists. I started the takeoff again from Runway X and the plane began to lift about 1;000 FT down the runway at 85 MPH. When the plane was about 20-30 FT off the runway; I began to retract the gear. Suddenly; I noticed a significant loss of lift and immediately lowered the gear while trying to maintain a landing attitude. The plane contacted the runway surface and the gear folded up in the plane as I was not able to get it locked in time. A propeller strike was heard and the plane was skidding on its main belly. I immediately pulled power; mixture; turned off magnetos; fuel pump; and main power. Upon coming to a stop; we evacuated the plane.