Bug#690902: Some things to try

[Erik]

Check /home/YOURUSER/.xsession-errors  or
/home/YOURUSER/.xsession-errors.old for relevant error messages. Post
them here. Take care as this log can frequently contain sensitive
information logged by some applications.

You could try creating a new user on the computer and try reproducing
the problem with it. If the problem does not happen then it could be
some settings under your other account.