Under the new Ubuntu 11.04 (Natty Narwhal), when you try and run MATLAB you'll get the following error
/matlab/bin/util/oscheck.sh: 605: /lib64/libc.so.6: not found
To resolve this problem, go to a terminal window (Alt + F2 from anywhere) and type
For 64 bit:
sudo ln -s /lib64/x86_64-linux-gnu/libc-2.13.so /lib64/libc.so.6
For 32 bit:
sudo ln -s /lib/i386-linux-gnu/libc-2.13.so /lib/libc.so.6
This should restore the missing library that was uninstalled during the Ubuntu update process.
This method only works for Ubuntu 11.04. For the newer release of Ubuntu 11.10 you need a slightly different fix, detailed here.