Error messages in sending/update thunderbird

when sending messages or forwarding e-mail have an error message as follows:-
"an error occurred while creating a message compose Windows. Please try again"
need some help in fixing this problem.

Regarding update of Thunderbird portable apps from 1.5.0.14 to 2.0.0.?my USB flash drive will not update although my "C" drive on e-mail Thunderbird is up to the current update (2.0.0.12). Would appreciate some help in this matter!!!