Finished the game after redoing a few of the puzzles. Much faster second time round.
But in case this helps:
Computer stats: Dell XPS 410, Core2Duo E6600, Win7x64, GTX 460, 3Gb DDR2
Game had progressed up until finding the warehouse. Did not have required tool to get key at time but was able to visualize it. Left warehouse thinking to backtrack to the only other existing locations (Ed's apartment, Police station, Edgetown). Went directly from Warehouse to Edgetown and was unable to leave. As Tramponline has mentioned, the exit arrow location is offscreen with no way to get there.