Inspiron 1525 Windows 7 HDMI issue

I have an Inspiron 1525 running Windows 7. I sometimes connect it to my Samsung LE46A558 through HDMI. Sometimes for no reason it seems like it doesn't find anything connected to HDMI, and other times it just reacts instantly when connecting the cable. I've checked for updated drivers for chipset etc but from what I can tell according to Dell Support, Intel and Windows Update I already have the most recent drivers.

Connected to the TV there is a IP-TV box from Motorola that works just fine on HDMI1, and the computer is connected to HDMI2. Doesn't matter if I remove the IP-TV box and run without it, the intermittent problem stays the same with the Inspiron and Samsung.

Sometimes when it works and I've started a film of any format in VLC the computer looses the connection to the TV (normally within 20 mins) and the picture switches over to the Laptop again.

Anyone familiar with this issue? Any good hints? Besides above mentioned it runs perfectly in Windows 7, only historical issue is that it used to crasch when unzipping large files via wireless network, but that dissappeared when I replaced the Belkin router.

Best Regards Henrik