11:32 p.m. on February 25, 2010 (EST)
tman--
I'm hoping not to offend, but must say I'm having a hard time figuring out what you're concerned about. I think I hear you saying you're very experienced and very comfortable in the back country, including areas very similar to Glacier. I also think I understand you to say you've got previous experience on your own out in the woods, but at other moments I'm not so sure.
As far as the park goes, it's risks are similar in type but variable in size to/from those of, say, Yellowstone. What I mean by this is that both have similar wildlife, general terrain features, etc. The exception to this is the obvious geologic difference--Yellowstone is, in essence, one big volcano, and has a tremendous amount of hot springs and other geothermal activity that Glacier doesn't.
I've been in and around Glacier and the wilderness areas that neighbor it several times, both in groups and solo. On foot and horseback. Haven't done it in winter, but have seen seasons change there. I've not been there in last 4-5 years, so can't claim truly current knowledge, but I've not heard of major changes, at least that I recall at present.
I'm comfortable with the idea of a solo trip in Glacier--for myself. Can't and won't speak for others. As for whether the local rangers "encourage" solo trips, I'm not sure that I'd make too much of a lack of encouragement. I'd be disappointed if they weren't conservative about such recommendations to those they don't know well.
If it's water-related hazards specifically you're worried about, then discussion with local rangers and others with specific and current (pardon the pun) info, along with proper guidebook consultation, should yield reasonable recommendations. A good general rule about potentially nasty rivers and such is to get up-to-date information about flow rates, water levels, and so forth from people who make it their business to know.
Glacier (and Waterton, and the surrounding areas) are absolutely stunning in their beauty. I consider the title of "Crown of the Continent" well deserved. If you do undertake a trip to Glacier NP, respect it, and follow regulations and the usual bits about LNT, trail behavior, and camping common sense. In which case, I expect you'll have a great time.