yes, but the '5 year clock' starts ticking again (unless you had establshed a ROTH IRA as well)
for anyone else out there reading this, this is an interesting recomendation implied by the regulations:
at the time someone starts a Roth 401(k) they should also establish a Roth IRA!!!!!!
see page 13/14 (assuming this shows the same format on your computer as mine, my print out from months ago is page 17) of the preamble to the regs
http://treasury.gov/press/releases/reports/roth402a.pdf