Use normal font size, please - that's fairly annoying to read
Have you tried creating a brand new user (that then has no other settings for Gnome than the defaults) and testing if that user also experiences the same? To find out if it's about your per-user configuration or maybe something system-wide..
And is there anything curious in X logfile? Did you try logging in with network enabled/disabled, does it make any difference (a wild guess, probably nothing)?