[S60Tom]

I am having a weird and intermittent fault with my HU-850 and 12 volt power outlets on my 2005 Volvo S60. There will be periods of around 6 weeks where there aren't any problems at all (apart from the fact that button illuminaton no longer works), followed by periods of around 8 weeks where the stereo unit is completely dead, the nav screen doesn't work and nor do the 12 volt outlets. There aren't any other electrical problems that I am aware of.

Could anyone potentially advise me if this is simply a matter of a dodgy fuse, loose connection or something potentially more serious?