This is a test.
http://www.C3VR.com
What browser are you using? (and what version?)
I just tried it two ways and both worked:
1. I typed the address into the message box, highlighted the text in the message box, clicked the Insert Hyperlink button, clicked the preview button on the insert hyperlink box and the OK button was still enabled, so I clicked it and the message was updated.
2. I put my cursor in the message box where I wanted to insert a link, I clicked the Insert Hyperlink button, typed in an address (without the http://) clicked the preview button on the insert hyperlink box and the OK button was still enabled, so I clicked it and the message was updated.
I'm thinking it is a browser issue.
I just did what you said using Chrome...
I typed in a link