When closing the last open spreadsheet, and returning to the main Libreoffice window, it is not restored correctly. I have found this bug with the same issue http://lists.debian.org/debian-openoffice/2011/10/msg00094.html and pictures here http://lists.debian.org/debian-openoffice/2011/10/msg00096.html I've not been able to find a similar bug submitted for libreoffice, I use Arch Linux updated to the latest versions from the repositories.
I have the same problem for a long time.
On further searching, I have finally found it to be an Intel driver bug https://bugs.freedesktop.org/show_bug.cgi?id=43649 *** This bug has been marked as a duplicate of bug 43649 ***
flag as moved, as referenced bug is not in our instance, and having duplicate without actual bug is not good for bugzilla's sanity :-)