try lock(youri2cdevice) and set the timeout lower.
also, do you have pullup resistors on your i2c lines? 4.7kohms are fine.
also try 100khz instead of 400 when talking to your device. you can change that when you found out what was wrong.
i have pullup my eeprom with 1k resistors.
i have locked my "myi2c" object but its still not working.
when i try to read the value of the selected register ,this message appears in output windows
Une exception de première chance de type 'System.ArgumentException' s'est produite dans Microsoft.SPOT.Hardware.dll.
Une exception non gérée du type 'System.ArgumentException' s'est produite dans Microsoft.SPOT.Hardware.dll
with some traduction, it will be somthig like this
A first chance exception of type 'System.ArgumentException' occurred in Microsoft.SPOT.Hardware.dll.
An unhandled exception of type 'System.ArgumentException' occurred in Microsoft.SPOT.Hardware.dll