Watin: BrowserNotFoundException on Browser.Attach<IE>(Find.ByURL(uri));

[Mervin]

Hello. I'm trying to find opened webpage by URI and to launch JS on it. I found some samples and wrote simple method. That's how it look:

private void GetHtmlCode()
{
    string uri = GetTargetURI();
    if(!string.IsNullOrEmpty(uri))
    {
        IE ie = IE.AttachTo<IE>(Find.ByUrl(uri));
        htmlCode = ie.Eval(JavaScriptToRun);
    }
    else
    {
        MessageBox.Show("Target page is not opened",
                        "Notification", MessageBoxButtons.OK);
    }
}

And there's a method for getting URI:

private string GetTargetURI() //проверка URL
{
    Regex reg;
    Match match;
    foreach(SHDocVw.InternetExplorer ie in shellWindows)
    {
        reg = new Regex(patternURL);
        match = reg.Match(ie.LocationURL.ToString());
        if (!string.IsNullOrEmpty(match.Value))
        {
            pageURL = ie.LocationURL.ToString();
            return pageURL;
        }
        pageURL = string.Empty;              
    }
    return pageURL;
} 

- so the URI is completely correct or empty.

The problem is

IE ie = IE.AttachTo<IE>(Find.ByUrl(uri));

always throws

WatiN.Core.Exceptions.BrowserNotFoundException: Could not find an IE window matching constraint: Attribute 'href' equals uri '%my_target_URI%'. Search expired after '30' seconds.

I've googled a lot, but still didn't find any solution :(
Can anyone help please?
Thanks.