Report server failed

Hi,

I have created a crystal report application using the template.
I designed a report using VS2005.
THe report loads fine. Report has as datasource an excel file (excel1.xls).
What I am trying to do is to switch the source on a click of a button.
The source is another excel file but different name (excel2.xls).

This is what I have:

Code:

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Code SnippetPrivate Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

CrystalReport21.SetDataSource("C:\excel1.xls")
CrystalReportViewer1.RefreshReport()

end sub

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This gives me an error. "Report application server failed"
Really have a hard time understanding why.
For info i have as imports:
Imports CrystalDecisions.CrystalReports.Engine

please please help me !