Serial to USB adapter issues

I am using a Dell Studio computer in a medical environment, which handles a medical device attached via USB to Serial adapter. There are 2 of these devices connected to this computer. The medical device needs to transmit data to a server.

The problem I am having, is one of the medical device seems to stop transmitting for no apparent reason. Usually a reboot will fix the problem, but this only temporary. I talked to the company that makes the medical device, and they say the problems lies with the USB jumping COM ports.

I have a couple of different PC, but with the same results.

Any suggestions would be helpful.