Network question

Hi! I know, this is a security board, but I have a network question and I can't resolve the problem. I have tryed all thing I know and I'm a network engineer. (I know what I'm do..) I always get collisions on my eth1, internal nic. Some pc's are connected over a half duplex hub. The nic's and the cables are ok. My questions is now.. Sometimes the data stream get frozen for about 3 or 4 sec. Can I push up somethink like windows size or something else I can try to get a better result? What I can adjust for earn a fast constant data stream without these connection errors?? Thanks for you help, Chris