It is shown that there are logarithmic operators in D-brane backgrounds that
lead to infrared divergences in open string loop amplitudes. These divergences
can be cancelled by changing the closed string background by operators that
correspond to the D-brane moving with constant velocity after some instant in
time, since it is precisely such operators that give rise to the appropriate
ultraviolet divergences in the closed string channel.Comment: Plain TeX, 5 page