3.9.1:
If you play in a team and all your units get killed you can no longer toggle to team chat mode.
I am not sure this was added by intention, because once my units are gone I can see without fog of war, but I don't like this behaviour. So I am not sure its a bug .
When it happened:
I played with Derek and david123 in a team and I was killed( all of my units ). After this I was not able to toggle to teamchat mode using the "H" key anymore.
How to reproduce:
I reproduced it later when by simply killing my partner units in a 2vs2 game ( I was running 3 clients and one server on the same computer ).
After this my "partner"-client was no longer able to switch to teamchat.