We have discovered a small issue where opening any window could address the wrong memory and possibly cause a crash. It is an obscure happenstance - it will only occur if you repeatedly open certain windows and opening a window may delay the actual crash until a long time afterwards, possibly an hour or so later.
This particular bug appears to affect Macintosh users mostly.
If you upgrade to this version of Theatre Manager, you will need to walk around and install it on all computers. Please be sure to check for updates using the 'Windows' menu to get this version.