Open to a worksheet where last saved

We're using Excel 2007 for a dispatch calendar at a school district. The workbook is for an entire year and the worksheets are by week.

We use the spreadsheet on a network where it is updated by multiple personnel. We had been using this setup for a year or more. Up until sometime last year when one of us opened the workbook it would position itself at approximately the week were last working with. Suddenly this stopped happening and it positions itself somewhere near the beginning worksheet (although the exact location differs from person to person).

Today I went back to one of the older sheets and opened it. It positioned itself at the end of the year so, it was doing what it used to do. I checked for a running macro but nothing was running.

No idea what caused the old desired behavior or how to get it back.

Thanks,
Dave