Comment 3 for bug 1116512

if its the 32 or 64 bit xsel should not matter
I saw such a hang once when the xsel support was added in 2.20, there is probably a deadlock somewhere when calling the external process
Unfortunately I have not been able to reliably reproduce it for debugging.

A workaround would be to remove xsel then it uses the mono built in copy/pasting which does not work in some applications but at least should not lock the program.