I'm getting this error after copying the new command line tools to / usr/local/bin: tm: you need to update this helper tool.
This is actually quite strange, since the protocol used to communicate with TM and the tool is at the same version as it has always been (so no combination of TM and the tool should give this error).
The only reason I see is that the TM started actually predates implementation of the protocol. Do you keep old versions of TM somewhere on your disk (even the trash counts here)?
Nope, no old versions on disk. However the issue mysteriously disappeared when I checked just now.
*crosses fingers*
- Ben