Somehow the curses stuff isn't working properly, which at the very least explains why keyboard input isn't working. Since the output seems normal when you turn off ncurses support (-T flag), that's the first problem I'd try to track down, but since I have no experience programming with ncurses, you may want to ask ckolivas for help on that one (unless someone else steps forward).
The output is the same without -T. It's the -D that was producing output.
Each of six threads was using 16-17%, i.e., about 100% total.
Here, each thread uses ~3%. I'd accept something higher if you're using dynamic intensity, otherwise you're probably being hit by the CPU usage bug. (BTW, how many cores?)
One core (Sempron 145). Maybe sometime I'll attempt to unlock the other, but it hasn't seemed important as I wasn't anticipating CPU intensity.
Personally, I'd try a newer version of Ubuntu, since those are more likely to be tested (I'd go for 11.04 or 11.10). Also, I'd really try using a pool since default output would be more verbose that way.
It's been my intention to use a pool; this solo experiment was just for intitial test and familiarization. I'd be shocked if adding a pool cures what seems to be a problem of the software hanging after a couple of seconds. But I'll add the pool just to be sure. And then, if I'm not shocked, I'll start researching the minimum-loss way to upgrade Ubuntu.