Dash electronics on the fritz...Any ideas???

[Enzodog]

My 09 X5 3.0 dash went out during 200 mile drive last week with frigid cold exterior temperatures in the teens. The nav, and radio went black while driving. Stopped at a rest stop for 20 minutes, got back in and the nav and radio came on on the restart. Got back on highway and it went back out five minutes later while driving. The next few days the nav and radio would still act up speratically. Now my wife says the seatbelt warning keeps sounding. Dealer found no codes in the computer. Dealer kept it for three days and could not replicate. Anyone experience the same or have any ideas? Thanks.