Can't for life of me remember where, but read somewhere, sometime, that the R-D1 did not like the heat very much. Have never had the opportunity to find out myself, its autumn here and had the camera a couple of weeks only.
EDIT: My D2X stopped working this summer, however. One summer afternoon, 30 degr C, outdoors, laying in the sun for maybe 10 minutes. Did not like it all. Metering, AE, and AF stopped working, though it did take pictures (of a sort). When cooled down worked a treat. Would have thought it was less succeptible to failure than the R-D1, but I'll have to wait until summer to find out.