You try to open a tab separated file in Excel and get error ‘Excel has detected that ‘test.txt’ is a SYLK file, but cannot load it. Either the file has errors or it is not a SYLK file format. Click OK to try to open the file in a different format.’
The file looks something like:
The problem is caused by the first field name, that is ‘ID’ in this case. Change it to something else and problem will go away.
Update: there is a Microsoft Support article “SYLK: File format is not valid” error message when you open file that describes this behavior.
Update 2: SYmbolic LinK (SYLK)