I've installed my second MU. The first has been a smooth ride. I hope the second will be equally great. The second is on a different domain, but with the same host. When I attempt to install plugins it usually fails and returns "An unknown error occured". The error is returned at varying stages, either when searching, when displaying plugin-info or when attempting to install. I've been able to successfully install Easy Contact and ICS calendar, no other plugins.
How do I troubleshoot this?