SPWeb has two sharepoint cross-site group collection, SPWeb.Groups and SPWeb.SiteGroups.

SPWeb.Groups returns collection of cross-site groups which has some permission on the site. So if you add group from a site without any permission on the site, then this group wont appear in SPWeb.Groups collection, but it will appear in SPWeb.SiteGroups collection.

You can not use SPWeb.Groups.Add method to add new cross-site group, you need to use SPWeb.SiteGroup.Add method for this purpose.

In addition to this SPWeb has a property AssociatedOwnerGroup, which will return the required SPGroup. You can iterate the SPGroup users to get the list of all owners of the site.

 foreach (SPUser user in web.AssociatedOwnerGroup.Users)
 {
      // .. list all the users                        
 }

Finding and adding group

SPGroup  group = GetSiteGroup(web, "groupName");
if (null == group)
{
 web.SiteGroups.Add("groupName", web.AssociatedOwnerGroup, null, "Test Group description");
}

private static SPGroup GetSiteGroup(SPWeb web, string name)
{
    foreach (SPGroup group in web.SiteGroups)
    {
 if (group.Name.ToLower() == name.ToLower())
 {
     return group;
 }
    }
 return null;
}

Few days before, I was having problem that after clicking on Export to pdf button / image, other controls of web part/user control stops working on the application page on WSS 3.0 environemnt that has RadGrid on it.

While the same thing was working on other asp.net application outside the sharepoint environment.

1st workaround (can be a solution)

The cause for this behavior is that there is a flag (named _spFormOnSubmitCalled) in SharePoint which prevents double form submition. This flag is set when the form is submitted and clear when the response is received.
However when exporting the response is redirected and the page is not updated, thus the flag is not cleared and page's postbacks are blocked.

In order to workaround this behavior you should manually clear the flag when exporting. This can be achieve, for example in export button's client click function similar to the following:

MyExportButton.OnClientClick = "_spFormOnSubmitCalled = false;"  

Above workaround will allow you to export multiple times, but all the other controls on the page were still not functional after the export.

2nd workaround (Not / Never recommended)

In your sharepoint master page, remove onsubmit attribute from your form tag

<form runat="server" onsubmit="return _spFormOnSubmitWrapper();"> 

and remove the onsubmit attribute.  This is what it looks like now:

<form runat="server"> 

3rd workaround (so far so good and implementable)

Add the following script to your webpart / custom control that need to have export and other controls functionals, rather then implementing the above workarounds
So here you go with the working solution.

<script type="text/javascript" language="javascript">

    //sharepoint postback to work after clicking on telerik export to pdf
    if (typeof (_spBodyOnLoadFunctionNames) != 'undefined' && _spBodyOnLoadFunctionNames != null) {
        _spBodyOnLoadFunctionNames.push("supressSubmitWraper");
    }

    function supressSubmitWraper() {
        _spSuppressFormOnSubmitWrapper = true;
    }
   
</script>

Hope this will helps.