Short Answer: When asked, always choose to 'Create a New Keychain'. If that doesn't work or isn't an option, you'll need to delete the keychain in question.
Long Answer: Macintosh users in large organizations frequently experience errors with regard to their 'keychains'. In macOS, the 'keychain' is a file in which the Macintosh OS stores any saved passwords for websites, shared network folders, and other resources. The issue is that macOS encrypts this file using the password that you're logged into the Mac with at the time you first log into it. For users in large organizations though, their passwords change regularly, but the password on this file doesn't change with it. After changing your password, when you log into a Mac that you've logged into previously, it will immediately try to open the old keychain file, and when it finds that it can't open it with the password you used to log into the system originally, it will ask if you'd like to a) 'Update the password' on the keychain file, b) 'Create a new keychain file', or c) Cancel. Cancelling doesn't work. The OS will keep trying to access the file. It's programmed to try to access it 5 times at a shot. Many things use it. Opening a web browser or a file browser will cause it to ask again (almost always the very next thing you do after logging in). If you attempt to 'Update' the password, you'll need to remember the password used when the keychain was created. It might be your most recent prior Lehigh password, depending on when you last logged into this machine. Frequently, in shared Mac labs, it's difficult to remember when you last sat down at this particular machine. The easiest option is always to simply 'Create a New Keychian' – you loose whatever passwords you stored, but in many ways, it's simply best not to store them on shared machines.