Please upload your crash reports or logs to https://gist.github.com or similiar sites, don't just paste it in raw!
If the issue is not a crash, please provide your fml-client-latest.log or fml-server-latest.log
Before reporting your issue, please make sure it have not already been reported.
Make sure you have the latest version of Harvest Festival, since your issue might already have been fixed!
Preferably provide us with what Forge version you are using.
If the issue is between Harvest Festival and another mod, please inform what version of the mod you are using. Also make sure the other mod is updated to latest version.
Thank you for reporting!