i usually don't bother with the "browser" and "page" and always add them to repository... and after that this is the code i tried, and it's working for me... and i'm assuming you're using Basic HTML view of Gmail.
Code:
Dim SendBtn
Set SendBtn = Description.Create()
SendBtn("name").value = "Send"
SendBtn("micclass").value = "WebButton"
SendBtn("type").value = "submit"
SendBtn("index").value = "0"
Browser("Gmail - Compose Mail").Page("Gmail - Compose Mail").WebButton(SendBtn).Click