Is that disk is multi-sessioned ?
If yes,
Then hope your friends not end the burning session....i,e
he not use/check the "Finalize Disc (No further writting possible)" option for your next use.
After enabling this option the CD can be viewed in any machine with every session and the whole burning session is end.
Sometime this type of problems occured.....like if you burn the disk in 3 session and not finalize yet ....in the mean time you tried the cd into another machine and it shows only first two session.
Or if the disk is not multi-sessioned then the disk is corupted and try to use a fresh one....