Thunderbird hickups

Hi, i wonder why Thunderbird sometimes lags bad. First i thougth it may
be the emailcheck, but since i put it 1hour, it still lags.
It is most appearend if i write a email and i’ll type and the word are
not appearing on the screen, or at least not right away.
Did someone else observe this behaviour?
Tech Check > 11.4 x64, LXDE, Thunderbird 5.0

Euer Komputerfriek Joerg
using LXDE on 11.4 x64 and happy with a cup of really hot coffee…