SerialPort.WriteTimout

I have been searching for info on what actually will cause a
WriteTimeout error to happen on a serialport object in net 2.0.  There
are lots of articles that talk about a Write operation not being able to
complete in the time allotted.  However, besides having a series of
bytes to be written that when taking into the account the baud rate
cannot complete in the allotted time, I can't think of another reason
for this error to occur - nor can I find reference to when it will
occur.

Any ideas or places you could point me, please?

Sincerely,
Peter