ptrace: Operation not permitted.
After a certain amount of bashing-of-head-against-wall and cursing-of-frustration-didn't-this-work-before activities, I did a bit of web searching, and found:
- gdb attach fails with ptrace: Operation not permitted
- Fixing problems on new Ubuntu version "Maverick Meerkat"
I'm not completely sure what to make of this, but the suggested workaround:
# echo 0 > /proc/sys/kernel/yama/ptrace_scope
(executed as root) seems to have done the trick, for now.
If this happened to be your particular nightmare as well, hopefully this saved you a few seconds of anguish...