The subject says it all. Linux strace, attaching to a running process with the '-p' argument, hangs about 80-90% of the time these days on me. Sometimes it will display the current system call in progress, sometimes it will not. I've tried sending all the standard signals to no avail. The only option is to suspend (ctrl-z) it or hard kill it. (-9 it.)

Does anyone have any suggestions, or have you seen this behavior before? Am I going nuts? Let me know what useful system information I can provide.

I'm not really sure what to tell you about WHY it's happening; but the same thing happened to me using strace to debug my window manager recently.
I'm not a big strace user, so I don't know much about it; however, using the -p argument caused strace (and my WM) to hang. I had to log out to kill the process.
Instead of using `strace -p` I changed the commandline like so, with the app I am stracing
as the last arg on the line (before the >>log):

and that worked fine I got the strace output to the logfile, and the WM ran as normal. I cannot explain why though but maybe you can do your strace this way too?

Sasha