If you receive an error like this, ie;
COM_Loadfile: Not enough space for maps/c_apartment2.bsp
COM_Loadfile: Not enough space for models/taller.mdl
This is a bug related to the original code from the Quake engine present in the Goldsource (Half-Life 1) engine, it can occur randomly for people many times, rarely or not at all.
Team psykskallar has looked into the issue but unfortunately due to the nature of the error, it is unlikely that it will ever be fixed as it would require the Half-Life engine source code, which has not been released and probably never will be. If upon further investigation the problem can be fixed however, it will be integrated into a new patch.
For now if this occurs, all you can do is restart the game. The team apologises for any inconvenience caused.