Unfortunately, there is a bug in the annual certificate review process that can affect the refresh of mouse/video connections. The bug only applies to certain use cases with VMConnect (i.e. Remote Desktop connections are unaffected) and there are two possible workarounds …
Mark Wilson explains this bug on his blog: http://www.markwilson.co.uk/blog/2010/09/extending-certificate-validity-to-avoid-mousevideo-refresh-issues-with-the-hyper-v-virtual-machine-connection.htm
