clutch/tranny problems???

i have a 2001 suzuki vitara with manual trannie. up until yesterday i have had no problems with it. but yesterday i went to a friends house drove there perfect and when i decided to leave i started my vehicle in neutral and tried to put it into gear no luck. the only way it would go in gear was if it was started in gear but then u could not change the gear it would only go into neutral i was wunderin if anyone knew what was wrong and how to fix it. thanks