Hi
Additionally to the mentioned problems, some ST7920 require an additional delay after writing a byte. I have fixed this in the attached version of u8glib. (line 117 in Google Code Archive - Long-term storage for Google Code Project Hosting.)
Frome some other reports, i also heard, that shorter wires improve the situation.
Oliver
u8glib_arduino_v1.09pre10.zip (692 KB)