Switch Statement in ISR

Hello everyone,

I am using the PGA400 from Texas Instruments (an 8051W processor) with uVision V4.02 and have traced an issue back to using a switch statement in the commBuff ISR. It appears to either have corrupted or overflowed some sort of variable (this might not be the case but that's what it appears to have done). I've replaced it from:

        switch (CommandState)
        {
                case (0):
// random code here
                break;
        }

to:

        if(CommandState==0)
        {
// random code here
        }

This seems to have fixed my problem for whatever reason. Is it a common practice to avoid using switch statements in an ISR or is this a Keil related issue? Any help you can give me would be appreciated. Thanks a lot!