Saving to Excel 2010 with ReportSmith V3.12

We use Reportsmith 3.12 as part of ADPs Enterprise V4 HRIS. We recently upgraded to MS Office 2010 and I am having issues when I save report results to Excel. The results are saved but when I open the file, click on the Enable Editing button, strange things happen to the file. We have to save it, close it, then open it again in Excel 2010 and things seem to be OK.
The Save As File Type has a *.xls file type in it but no *.xlsx. Is this something I can control through the Reportsmith INI files?

Any help would greatly be appreciated.
Thanks, Theresa