Error: Can't open D:\GFXbuilds\maps\dod_d-day.p0

wat does that mean? i just recieved it when i try compiling my map. it gives me an Windows XP style error. any help? no errors in hammer...

The p0 file was not generated by bsp.exe because there's an error in the rmf. For example a brush-based entity partially covered with the clip texture.

May i suggest to check what you did in Hammer after the previous compile which was ok. If this fails, compile the map section by section (select say the spawn, copy and paste in a new map and compile). Yes it is a heavy method but there's no other alternative.
Another reminder to compile the map as often as possible. easyer to track errors.