Recent changes in wpi(4) require an upgrade of the wpi-firmware package to revision 2.14.4. As usual, you can find a prepackaged version of the firmware at: http://damien.bergamini.free.fr/packages/openbsd/wpi-firmware-2.14.4.tgz
or you can download it directly from: http://www.intellinuxwireless.org/ and copy it to /etc/firmware/wpi-3945abg The driver will stop working if you don't upgrade the package. Damien