problem with graphicsMagick and Apache

Hi All, Might not be the correct place, but I hope someone in here can help me with this problem. running this from command line will execute correctly: gm convert source -resize 600x800 dest but running the same from within a script using exec() causes the threads to hang, restarting apache with graceful, causes the threads to be finished and the images are stored correctly. code : exec('gm convert '.$source.' -resize 600x800 '.$dest); And I did try with shell_exec() also, no difference. Can anyone give me a pointer as to why this happens ? Regards, Toke Herkild