I have a problem with the unsigned values that in previouse version works well:

task main()
{
nxtDisplayTextLine(1, "%d",255);
while (true);
}

This code shows in the NXT window: 1680147487

and with this code:

task main()
{
byte a=255;
nxtDisplayTextLine(1, "%i",(unsigned int)a);
while (true);
}

The result is: -1

The compiler is calculating this correctly. a "byte" is the same as a "char" which has a range of -128 to +127. When you assign a value of 255, it will overflow and end up with a value of -1.

Here is proof from a GCC compiler which exhibits the same behavior. http://i.imgur.com/BQQ7yQZ.png

Try using a ubyte instead which has a range of 0-255 and will be able to store your value.