trouble with NHD-0420D3Z-FL-GBW-V3 using I2C

[phills]

I am using a NHD-0420D3Z-FL-GBW-V3 with an Arduino Uno using the I2C interface. It mostly works, but occasionally (about 1 in 50) a character is dropped. When I reduce the I2C clock rate in the Arduino from 100Hz to 50Hz, the problem is solved. Is there a timing problem in the display's driver chip?
I looked at the I2C signals from the Arduino at 100kHz and everything looks good, in accordance with the I2C specification. The problem also occurs at an I2C clock rate of 75kHz.