Firefox opening a doPostBack call in new tab

Question

Here's an odd Firefox behavior. I have developed a simple application in .Net 3.5. I am using firefox 3.5.3 and so is my colleague. On one of the pages, I have a simple partial postback that hides one panel and displays another. When I click the link, the application behaves as intended, but when my co-worker does it, firefox opens a new tab with the "javascript:dopostBack(...." text in the url locator. She can then close the tab, and the application will work as intended. The second time she clicks the link, the one panel is hidden and the other is displayed.

The link is a LinkButton object sitting in a grid view. It looks like this:

                <asp:LinkButton runat="server" OnCommand="SelectSite" CommandArgument='<%# Eval("SiteID") %>'
                Text='<%# Eval("SiteUrl") %>' ID="btnSelectSite" >
                </asp:LinkButton>

By clicking the link, the user is selecting a web site.

The select site method looks like this:

    protected void SelectSite(object sender, CommandEventArgs e)
    {
        ShowEditPanel();   
        m_SiteID = e.CommandArgument.GetInt();
    }

Shows the edit panel, and sets the member variable. The form gets loaded on PreRender.

Any ideas?