I haven't bothered to look into the issue, because I don't use it often enough for it to matter, but when using JEmplode with the Solaris box on my desk and
java version "1.2.2"
Solaris VM (build Solaris_JDK_1.2.2_05a, native threads, sunwjit)

tcpdump reports every packet I send has a bad tcp checksum.
[bad tcp cksum 1c56!] 3155:3155(0) ack 1914230 win 24820 (DF) (ttl 64, id 43498, len 40)

I probably have newer java somewhere, and again, I think this is the 2nd time ever that I used JEmplode on this machine, so I don't think I even care anough to see if it's Java, JEmplode or the kernel. (I'd guess Java if I could guess how).

It's just "interesting".

That is kind of interesting .... I imagine that is a lower level than I have any control over, and would guess that it's that version of the java VM on solaris. Maybe try a 1.4 VM on there sometime and see if they've fixed it?