Trying to open CSV file that my app had generated kept causing the following message to appear in Excel:
Excel has detected that ‘balhblah.csv’ is an SYLK file, but cannot load it. Either the file has error or it is not a SYLK file format. Click OK to try to open the file in a different format’ , you may also get the message SYLK: File format is not valid
After many hours of pulling my hair out trying to work it out I discovered that if you make the first letters “ID” of a text file Excel incorrectly assumes you are trying to open an SYLK file (whatever one of those is!).
Hope that helps!
PS Microsoft have a page on this now… http://support2.microsoft.com/kb/323626