OutputTo creates excel files that cannot be read

[RedGBarn]

I have created an output from a form

DoCmd.OutputTo acOutputQuery, "query name", acFormatXLS, "file.xls"

The spreadsheet creates OK, however when I link another spreadsheet t
it it gives me an error "Unable to Read File" and will not update - i
I add a random character in a non relevant cell and resave the file th
problem goes away

Any ideas?

Many thanks
Darre