[Spenuela]

When I try to play it gives me this message

Could not load in 2_CommandBrief-mb!
KERNELBASE.dll! ReleaseMutex + 148 bytes
KERNELBASE.dll! WaitForSingleObjectEx + 95 bytes
kernel32.dll! WaitForSingleObjectEx + 67 bytes
kernel32.dll! WaitForSingleObject + 18 bytes
fs2_open_3_6_12r_INF.exe! <no symbol>
fs2_open_3_6_12r_INF.exe! <no symbol>

and when i hit debug, it takes me to a briefing screen where my mouse does not work.

[General Battuta]

Easy fix. First, try going into the launcher and turning your screen resolution up above 640x480.

Second, please run a debug build (ends in -d instead of -r) until you hit the error, then go to FreeSpace2\data and post the fs2open.log file found there.