This morning I upgraded from Toucan 2.2.0 to 3.0 - standard stuff, no errors or issues.
Now when I start Toucan, the splash screen appears then there is a pause after which Windows pops up a box saying "Toucan.exe has stopped working".
This is with Windows 7, 64-bit.
Have downgraded back to 2.2.0 for now. That is working OK.