Ok so the bike I have is a 7 speed. I know its a freewheel because I asked a bike mechanic about it plus I can physically see that its one unit not a bunch of loose cogs like a cassette. As for being in Denver I do leave my bike out on my back patio but the patio is covered and never gets wet. To add to that this problem started last summer when I was riding in 80-100 degree dry weather. Also when it first started happening it would only do it under high load say like when I would be climbing up hill in the the highest gear and would also occassionally cause my chain to fall off between the lowest cog and the bike frame. I found that if I lubed it up before rides and in the middle of longer ones the chances of this happening would dimish. This would all again seem to indication that it is infact the freewheel?