Since installing HL2 it seems I can't seem to run Hammer any more; it gives the error on loading. Any thoughts? I know it's related to loading the GCFs but I can't do anything to get around it.
MountFilesystem( 203 ) failed: SteamMountFilesystem(2452,203,0x4fafbfc=,0x4fafd0c) failed with error 104: Not subscribed


