The first thing I would check iron. In ubuntu in the boot menu has memtest86. From experience I can say that some bugs appear after half an hour of testing (depends on CPU speed and memory, as well as its volume), some have heard, after a day of testing.
Then run strace on the falling team.
Even slazil would manually on the website packages.ubuntu.com and if there is a newer version of libc, I tried to download and install it manually (dpkg-i, dpkg if not falling).