USB-to-serial adapter no longer working in 8.0-RC1

Last May, Hans Petter Selasky fixed up the umct driver for 8.0-CURRENT 
(http://lists.freebsd.org/pipermail/freebsd-current/2009-May/007125.html). 
After updating to 8.0-RC1 I find that the driver has a new problem.

Testing with cu(1) and a modem, I can see by watching the lights on the 
modem and on the usb-serial adapter that it still asserts DTR and sends 
and receives characters properly, but no characters reach the terminal. 
That seems to be the only problem: characters from the attached serial 
device seem to disappear before reaching whatever program has the serial 
device open.  But strangely enough, power cycling the modem results in a 
few "line noise" characters appearing.  Perhaps the driver is no longer 
responding appropriately to DSR?

Any insight or troubleshooting clues would be much appreciated.

-- 
Greg Rivers