Hi,
Do you get a specific error message (lower left Status Bar) before or when this happens? Does it happen for all files, or just a specific file? If it's just a specific file, can you please either post a copy of the file here or send it to me at
support@notation.com and I'll take a look at it.
If it's occurring for all files, then you may need to try reinstalling the software.
ttfn,
Sherry