Try closing Altru and clearing your Internet browser's cache. Then log back into Altru and see if the issue is still occurring. You can clear your cache by following these steps: How do I clear my browser cache, cookies, and temporary Internet files

If you are entering Seasonal Information on a constituent's address, you will receive the error if you enter one of the dates as 2/29, which would only apply to leap years. Adjusting this to 2/28 should resolve the issue.