InfoPath Dev

Hi there!

I created a web service with two methods:
one for checking out a document and one for deleting a document.
I tried both methods with a test Windows form application and they work fine.

I published the form with full trust and a certificate, so the security should be fine.

However, when I call them from managed code within the infopath document (in exactly the same way), the checking out method always reports/throws an exception that the file is already checked out. The delete method deletes the document, however, when I want to submit the document again, I get an error message that I can not overwrite the file (I don't want to give that permission to the submit data-connection).

The methods look like this:

public string DeleteDocument(string page, string folder, string file)
{
    try
    {
        SPSite site = new SPSite(page);
        SPWeb web = site.OpenWeb();
               
        SPFileCollection delFiles =    
         web.Folders[folder].Files;
        delFiles.Delete(file);
               
        web.Close();site.Close();

    // ...

public string CheckOutDocument(string page, string outFile)
{
    SPSite site = new SPSite(page);
    SPWeb web = site.OpenWeb();
    SPFile file = web.GetFile(outFile);

    if (file.Exists)
    {
        if (SPFile.SPCheckOutStatus.None == file.CheckOutStatus)
        {
            try
            {
                file.CheckOut();
                web.Close();
                site.Close();

    //...

I call the methods with:

SharePointService.SPService _svc = new SharePointService.SPService();
_svc.Credentials = CredentialCache.DefaultCredentials;
string result = _svc.CheckOutDocument(page,thisXDocument.URI);

Does anyone know a reason for this odd behavior?
Would be great if I could get this work ...