This one really puzzles me, as the code looks completely harmless.
IE8 halts script execution with a message:
Not implemented. map.js line:66 cha
IE 8 has a great javascript debugger. You might want to add a breakpoint somewhere before the error and step through the code to see if something is strange with the data. IE8 is picky with trailing commas in lists which might be why you only get the error in it. You can pull the debugger up with F12, click Script and choose start debugging. You can add a break point by clicking on the margin where the line numbers are.