So... I have created a JIRA entry. VWR-27041, for the problem I have in which the SL client allocates all available RAM and then crashes. The symptoms have shown up before, vide VWR-2840; for all I know it's the same issue.
I have learned one thing: it doesn't look like it's a 64-bit versus 32-bit issue. I installed 32-bit Linux (Ubuntu 11.10 Beta 2) on a spare computer, and it did the same darn thing--allocate all the RAM in sight and then crash. (It was nice to be able to hear streaming audio, though.)
I hope someone will find a solution; this is getting old.
UPDATE: It's now been assigned to a Linden, and "fix version" is now "Sprint 29"--we'll have to see how hard it turns out to be to diagnose. I will provide any info I can. I'm hopeful that it will finally get killed, which will just leave the job of pleading with some TPV folks to incorporate the fix.