The problem may be with your specification of the minimum size of
exterior basins. Exterior basins are first order basins. You give
the minimum size by specifying "t=1":
/usr3/grass4.0/etc/water/seg el="elevation@PERMANENT" de="lakes@PERMANENT"
t=1 ba="basin1" ar="relate1" ac="accum1"
^^^
I don't know what your units are, but if this is in meters, then you are
allowing the computer to make drainage basins that are only one sqare meter!
A more practical value would be on the order of 1000000 square meters or
more. Then your first order basins would be a kilometer on a side, or
larger. Otherwise, your program will run forever.
John Stamm
Interactive Computer Graphics Lab