I have the same problem with 9.1 amd64 (Full USB distro).
Got to press twice from the "System Manager -> Tasks -> Download Kernel Sources" and there is nothing on /sys (I try to build form source an nvidia-driver and it complains).
Also tried trough the sysinstall tip with no success: no "ssys" distribution. Also the FTP source searches with suffix "-p4" which is not found on the FreeBSD servers.
P.S. Workaround found. I copied the kernel source code from the 'sys' folder found inside the USB dist/extras/components/src.txz
Last edited by Rado; 07-19-2013 at 03:09 PM.
Reason: Workaround founded.