Regex problem - Match.Index

[hwait]

I've a string (got it via WebRequest):

<td class=maintable noWrap bgcolor=#666666><b><font
color=#ffffff>HDR A </font></b></td>
....
Inner text A
....
<td class=maintable noWrap bgcolor=#666666><b><font
color=#ffffff>HDR B </font></b></td>
....
Inner text B
....
<td class=maintable noWrap bgcolor=#666666><b><font
color=#ffffff>HDR C </font></b></td>
....
Inner text C
....

The code is:
Regex headers_reg = new
Regex(@"<td[^>]*><b><font[^>]*>(?<header>[^<]*)</font></b></td>",RegexOptions.Singleline);

Match match = headers_reg.Match(page);
while (match.Success)
{
value = match.Groups["header"].Value.Trim();
startPos=match.Index+match.Length;
match = match.NextMatch();
}

So, this code usually works fine but sometimes it made strange thing.
The startPos in the first match became equal to the page.Length,
but the value is correct - "HDR A ".
After this obstackle the headers_reg doesn't match any strings below.
So, I have only one correct match - first, and startPos=page.Length;

Does anybody can help?

Thank you.
Nikolay