Now you've got me curious...
Did you have the same internet access both times? (OmniPlan does check in with our server periodically to ensure you're running the latest version, unless you turn that option off.)
If it gets stuck again, take a sample of it before force-quitting and send us the sample. We might be able to pull something from that.
To take a sample:
1) Open Activity Monitor (in Applications/Utilities)
2) Select the stuck OmniPlan process from the list
3) Click "Inspect" in the toolbar; a new window will appear
4) Click the "Sample" button in the new window (and wait several seconds)
5) When it finishes, click "Save..." and save the file somewhere you can find it again
6) Attach the file to an email and send it to
omniplan@omnigroup.com