I'm confused as to why you have
Code:
For j = 1 To 6 
  .ChartData = arrData 
Next j
in there. That will just assign the same array 6 times. And yep, that's definitely why you got a type mismatch.

I have a pretty good reference book on VB controls, with about 30 pages on the MSChart control. If you want me to look something up just say (I'm not gonna type all 30 pages up though )

I'm not too sure why you have a 2-dimensional array but a Columncount of only 1. I've not used charts much yet (just about to start in fact) but I would have expected a Columncount of 2. Maybe, if there's values left over, the control is using them to make your extra lines?

By the way you can put your code in code tags to preserve formatting and add the VB colours. Just put the words 'code' and '/code' in square brackets [ & ] at either end of your block of code.