Narrative:

I was initially cleared from company ramp to taxi to runway 9. I taxied to the run-up area for runway 9 and commenced routine run-ups. After completing my run-up and prior to further taxi, ground control contacted me a second time without my prompting and I heard the controller tell me I was cleared to taxi to runway 9 (the active runway). I proceeded to taxi onto runway 9. As I crossed the hold short lines, I switched to tower. After crossing the hold short lines. Tower contacted me and told me that I had not been cleared to taxi onto the active runway, and that this was a runway incursion. This did not affect any other aircraft in the class D airspace (ie, no other aircraft was required to abort or go around).

Google
 

Original NASA ASRS Text

Title: PIPER PA28 PLT BELIEVED THAT HE WAS CLRED ONTO THE RWY FOR TKOF AND CONSEQUENTLY CROSSED THE HOLD SHORT LINE AT FPR.

Narrative: I WAS INITIALLY CLRED FROM COMPANY RAMP TO TAXI TO RWY 9. I TAXIED TO THE RUN-UP AREA FOR RWY 9 AND COMMENCED ROUTINE RUN-UPS. AFTER COMPLETING MY RUN-UP AND PRIOR TO FURTHER TAXI, GND CTL CONTACTED ME A SECOND TIME WITHOUT MY PROMPTING AND I HEARD THE CTLR TELL ME I WAS CLRED TO TAXI TO RWY 9 (THE ACTIVE RWY). I PROCEEDED TO TAXI ONTO RWY 9. AS I CROSSED THE HOLD SHORT LINES, I SWITCHED TO TWR. AFTER XING THE HOLD SHORT LINES. TWR CONTACTED ME AND TOLD ME THAT I HAD NOT BEEN CLRED TO TAXI ONTO THE ACTIVE RWY, AND THAT THIS WAS A RWY INCURSION. THIS DID NOT AFFECT ANY OTHER ACFT IN THE CLASS D AIRSPACE (IE, NO OTHER ACFT WAS REQUIRED TO ABORT OR GO AROUND).

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.