Herbylyn;
Just to check this issue, I "downgraded to the last firmware from
http://mtbest.net/setting-up-navi-GT31.htm, but then something strange happened...

No matter what I tried, constantly got that #@!* "error 1" thing.
So I thought, something is wrong. Before I tried to update, I configured the GT-31 by reading this article on
www.locosystech.com/download/handheld/GT-31/GT31_Manual_20090402.pdf, after those settings.....no update possible through the updater.
Therefor there must be something with the settings. So I returned to
mtbest.net/setting-up-navi-GT31.htm and fixed all the settings again !
Believe it or not; after that, I tried the update again and VOILA...downgraded to GT31_FW_V1.3B1123T.ZIP (nov 2009 ).

After that, I did a new upgrade to GT31_FW_V1.3B1015_DVT3.ZIP...worked again.
Still....if you want the new large font and some more choices in the misc menu, I would say,go back to the GT31_FW_V1.3B1123T.ZIP.