On the Network page, start typing a user name e.g. "Dav", a list of users matching the text will show up. I should be able to select a user to follow. If I select a user by using the Up/down arrow and the Enter key, it is not a problem. Select a user with mouse click sometimes doesn't populate the textbox.

This can cause a related bug http://jira.atlassian.com/browse/CONF-16852 probably because it was trying to follow a user with the user name "Dav" that doesn't exist.