The fact is that an Objective-C array contains objects, it cannot contain primitive types. The tag argument is an integer, and you're passing an object instead (probably you got a compiler warning). I suppose that the object is a NSNumber, so you should take it's value calling the intValue accessor:
CCLabelTTF *progressLBL = (CCLabelTTF *)[self getChildByTag:[dataInfo objectAtIndex:0].intValue ];
Which with the newer compilers syntax can be translated like this:
CCLabelTTF *progressLBL = (CCLabelTTF *)[self getChildByTag: dataInfo[0].intValue ];