Print jobs stay in queue

I have an HP4000 printer set up on my network that is connected to a jetdirect print server. When a user sends a print job to the server, the job prints but stays in the queue. Eventually the queue gets VERY full and will not accept any more printjobs. I have 3 other HP4000’s on the network and none of the others have this problem. I have been unable to find a resolution on HP or Microsoft’s website. Any help would be appreciated. Thanks.