The following code crashes robotc when I try to download it to my NXT, at the point where normally the start/stop pop up appears it just closes down the the application. I've tried loading some of the sample progs. and they are fine. Any help would be much appreciated.

not bad for the first try, check the following points:

for (iLoop=0; iLoop<=50; iLoop=iLoop+=10)

I assume you wanted to write iLoop = iLoop + 10 then you might have found the more compact way iLoop += 10. In this context it causes only redundancy and no harm, but does not look nice

The following is however surely will not work:

do while (nMotorEncoder[motorA]<=iLoop)
{
motor[motorA] = 75;
motor[motorC] = -75;
bRead = true;
}

there are two types of conditional loops. the first one is the
while( condition ) { core of the loop }
the other one is
do { core of the loop } while ( condition );

your code is the second form without any action within the loop core.
the RobotC will infinitely repeat the do while(...) loop since the motor is not working.

May I propose an alternative architecture:

start the motor (e.g. motor[ motorA ] = required power)

make a loop that waits for the motor encoder to reach the target

stop the motor by setting motor[ motorA ] = 0

also, if you are a beginner, it helps a lot if you have a piece of paper with columns for the variables and try to play the role of the computer.

I would like to call your attention that robotc is very fast.

what you will see that your robot rotates a bit (more precisely, the motors make almost a half turn, the B in opposite direction) and then it stops.

I can't tell you why the robotc crashes but that requires another investigation (have you tried to compile and download sample programs?)

Elemes,
Thanks for the advice on the loops, it's most welcome.My main problem is still the crashing, yes I've already tried the sample programmes and they work fine. Thanks again.

When doing function calls in ROBOTC, you may want to call them like functions, as ROBOTC might confuse your function names as reserved words... Also, you do not need just a "do" loop.

I've edited your code just quickly. I'll test it in a bit if I get a chance:

ROBOTC compiler was not generating error messages for some of the incorrect syntax in this program. Things like:
1. Bad "do while" syntax (twice)
2. Function name without "()".

These errors meant that the executable file was bad because there was no code generated for task "main".

The fact that task main was empty was the ultimate cause of the crash.

ROBOTC compiler has been fixed to generate error messages.