About a year ago, I used a beta of Excel 2007 to save a bunch of worksheets in Excel 2003 format to avoid compatibility issues. Never gave it a thought in spite of some warnings later on about not being able to open in later versions of Excel 2007.
This morning, I tried to open several of these in RTM version of Excel 2007. Got a nastigram display box that these xls files were incompatible and I needed to install the beta version of Excel 2007. WTF?
I have Excel 2003 on my corporate laptop. Took a USB flash drive with the files in question over to that laptop. Absolutely no complaints from Excel 2003 and they opened just fine. I resaved them in Excel 2003 and replaced the ones that wouldn’t open. Mission accomplished.
Excel 2007 is pretty dumb if you ask me.