Invalid FCS files from Cellquest

I use a FACScan with Cellquest 3.3 on a Mac running OS9.2.2.  I do my 
analysis with WinMDI.  Today when I tried to open the data files with 
WinMDI it says:

Invalid file or not a standard FCS1.0/FCD2.0 file format.

I have rerun the samples to generate new files, tried opening them on a 
different computer and transferring the files by disk and email to no avail.

The flow cytometer has been fairly idle recently, but I am not aware of any 
changes since I lasted successfully used it and performed my data analysis. 
Another user had the same problem yesterday.

Any suggestions?

Thanks in advance,
Trevor