Yes, it's very likely the fuse, because the slides are dirty and it takes too much current to move the roof, so the fuse goes. You may be able to get it closed by replacing the fuse. I think they are in the engine compartment under a black plastic cover next to the brake booster.
Don't use just anything to lube it, go to a dealer (ouch!!) or a good independent mechanic and have them use the MB sliding sunroof paste. This isn't typical grease. You won't want to buy it, comes only in a 1 lb can, costs $52 or so. Cheaper than repairs, but you would never ever use it up!
If you use anything else, you risk ruining the pads and slides, and this is EXPENSIVE -- they cost almost as much as the replacement lift angles did! Mine on the 300D was all screwed up, mostly from bad grease and neglect.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!