Printing envelopes does not print to correct size. A #10 envelope prints to A4 size. Other size envelopes all print incorrectly.
This bug was introduced in OOo 3.2. I filed a OOo bug report http://openoffice.org/bugzilla/show_bug.cgi?id=116063 with details. It was marked as a duplicate of http://openoffice.org/bugzilla/show_bug.cgi?id=108961 which has been marked as fixed for OOo 3.4
However, the only "fix" in OOo 3.4 beta 1 and LibreOffice 3.4.2 it that a #10 envelope now prints to A4 size paper instead of to letter size paper.
*** This bug has been marked as a duplicate of bug 33778 ***