Thanks again for the triage report, friesoft. The other "solutions" floating around didn't work, but i copied the database

/home/user/.rtcomm-eventlogger/el-v1.db

to MyDocs and then connected up to my comp in mass storage mode. I opened the db file with sqlitebrowser as suggested and, sure enough, found that the SMS right when things went bad was missing the remote_uid field, with the flag still 1 (unsent). I changed the two fields, saved, disconnected, and copied the db back to its location in home. After a reboot, all is well.

Hooray!