sberlin: THANK YOU for your explanation and instructions to reenable the JIT! I hadn't been suffering the failure-to-start problem, so ever since the JIT was disabled by default, Limewire's hashing thread -- and by extension Limewire itself -- had become almost completely useless (several hours to hash a 40-megabyte file, and no, that's not an exaggeration.)
Reenabling the JIT hashed that 40-megabyte file in less than a minute. I'm on a 233 MHz G3 Powerbook, with 384 MB of ram.
I think the JIT is more valuable on old machines than you believe it is!
Limewire is usable again. Thank you!