Ian Mallett wrote:
The driver is: 8.552.0.0 (10/28/08). 
I have gl_FragData[n] just for MRT purposes.  Good to know about these issues though.  Why is it an issue?  Just to be annoying?

My guess it is a bug in the driver since other drivers have no issues with it at all (that I know of). And it wouldn't make sense either, to restrict the programmer to only use const integers to index language-specific arrays.