[ros-users] "could not find common time"-problem with tf

Hi everybody,

I get a strange error when I try to do a transformPose:
[ERROR] ... Could not find a common time /base_link and /map
and
[ERROR] ... Could not find a connection between /base_link and /map
because they are not part of the same tree.

But when I start tf_echo /base_link /map there is a proper transformation.

The error occurred suddenly when I started a launch-file which did
work without any problem at the last startup.

'rosrun tf reset_time.py' solves the problem for a short time, but
after some successful calls of "transformPose" the error is back again.

Any ideas?

Greetings from the RoboCup German Open in Magdeburg,
Sabrina