Drat!
Stoney, hold on to the spoon for the mo mate!
Lurk R, confirm that the lines:
rename c: \folder1\*.xls *.csv
rename c: \folder2\*.xls *.csv
rename c: \folder3\*.xls *.csv
<repeat for all folders>
....are all that exists in the batch file and nothing else. I just tried it and it worked for me without problems.