Network with GB svitch and a speed of file issue

To use some DL2´s connected with a switch to our network make the CMA to drop the connection randomly (mac & pc), we have stabile network and seem not to loose any ip´s on the computer, but the connection seems to loose the DL2 randomly.....any ideas? When conntected directly, no problems (but a hazzle to load files in several units)

Also we get speed issues ONLY with the custom content, when using a file it starts in normal speed, then suddenly it starts to speed up to the maximum without any cue ( yes, the content are properly made and are m2v´s), PAL.
Anyone have a hint here?