Crashing with no errors

I start a normal server , A regular multiplayer server , everything goes good after i reinstalled Gmod , i launched nukes , bombs , tons of props and npcs for testing , all came out with LITTLE lag on the nukes and nothing else.

But when i invite any of my friends or when anyone out there comes in my server , Boom , Unknown error comes up.

and i mean Literally , an unknown error. there is no error at all , and though the gmod crashes time after time…( 6 times to be exact )

My friends suggestions
Reinstall Gmod ( Fixed the 5 min crash , when i start a multiplayer server , it doesnt crash in 5 min )
Restart steam ( Nothing )

any more suggestions? Or may the Facepunch helpers please tell me what is going on here? Do i have to buy my own server ? And do i need a special program for that to work , please answer back , my friends like my USED TO BE ON servers.