With the change to TexLive, many of the packages that were part of the old tetex, are now separate packages. It appears that dvipdfm is now a separate package and if it is not installed then the dvi -> PDF generation method (which does appear by default in the Lyx menu) using the dvipdfm option fails with an error message. To fix this, the lyx package should have a "Requires: dvipdfm" added for F-9 and later.
Ping? This should be a fairly simple fix.
Added to rawhide, and lyx-1.5.6-2 build (coming soon to updates).
lyx-1.5.6-2.fc9 has been submitted as an update for Fedora 9
lyx-1.5.6-2.fc9 has been pushed to the Fedora 9 testing repository. If problems still persist, please make note of it in this bug report. If you want to test the update, you can install it with su -c 'yum --enablerepo=updates-testing update lyx'. You can provide feedback for this update here: http://admin.fedoraproject.org/updates/F9/FEDORA-2008-7019
lyx-1.5.6-2.fc9 has been pushed to the Fedora 9 stable repository. If problems still persist, please make note of it in this bug report.