Problem with XML Expansion Pack in Excel 2003 and .NET2.0

[Mk23]

Hi

We have a Excel Extension using XML Expansion Pack with Smart Documents.
Originally the Application was written for .NET1.1. Know we decided to go to
..NET2.0 with all our applications. So also with this one.

But now we can't start the application under Excel. Every time we start the
excel with this extension we get the error:
"The XML expansion pack or the Smart Document program is missing or invalid.
Contact your system administrator or the person who provided this document."

I searched the web but didn't find a lot of hints.
I checked the XML Extension Definition file with the tool in "Office 2003
Smart Document Software Development Kit (SDK)"

Checked the Application with the hints from
http://msdn.microsoft.com/en-us/library/aa194077(office.11).aspx without
further success.

The XML definition looks like:
<?xml version="1.0" encoding="UTF-8" standalone="no"?><manifest
xmlns="http://schemas.microsoft.com/office/xmlexpansionpacks/2003">
<version>1.0</version>
<updateFrequency>20160</updateFrequency>
<uri>urn:Ch.Timeware.AbsenceReportExcelTaskPane</uri>
<solution>
<solutionID>{BDE88D2F-FA67-4890-A674-A2BEE936A1A7}</solutionID>
<type>smartDocument</type>
<alias lcid="*">Absence Report</alias>
<documentSpecific>False</documentSpecific>
<targetApplication>Excel.Application.11</targetApplication>
<file>
<type>solutionActionHandler</type>
<version>1.0</version>
<filePath>Ch.Timeware.AbsenceReportPane.dll</filePath>

<CLSNAME>Ch.Timeware.AbsenceReportPane.ExcelTaskPaneSmartDocument</CLSNAME>
<managed/>
<runFromServer>True</runFromServer>
</file>
</solution>
<solution>
<solutionID>schema</solutionID>
<type>schema</type>
<alias lcid="*">Absence Report</alias>
<file>
<type>schema</type>
<version>1.0</version>
<filePath>AbsenceReport.xsd</filePath>
</file>
</solution>
<Signature .........

Does anybody has a further hint for me?

Regards Thomas