CoverageReport.xsl being used by another process?

I'm getting this output in my ccnet build report:

[exec] -----------------------------------------
[exec] NCoverExplorer.Console 1.3.6.2004
[exec] (c) 2006 Grant Drake
[exec] http://www.ncoverexplorer.org/
[exec] -----------------------------------------
[exec] Using default .config file: C:\Documents and Settings\sys_swdev\Application Data\KiwiDevelopment\NCoverExplorer\NCoverExplorer.config
[exec] -- Options:
[exec] Project Name: Unknown
[exec] Acceptance%: 95%
[exec] Sort: Name
[exec] Filter: None
[exec] Xml Report: CoverageReport.xml
[exec] Html Report: N/A
[exec] Report Type: ModuleSummary(1)
[exec] Merge To: N/A
[exec] Exclusions: (No report footer section)
[exec] -- Loading file: c:\nunit\bin\coverage.xml...
[exec] -- Calculating coverage and applying exclusions...
[exec] -- Sorting...
[exec] -- Coverage file parsing complete.
[exec] 39.9% coverage, 3210 unvisited sequence points in 1 file.
[exec] -- Applying command line options ...
[exec] -- Generating summary report...
[exec] The process cannot access the file 'c:\nunit\bin\CoverageReport.xsl' because it is being used by another process.

I can run ncoverexplorer.console just fine from a DOS box on the build machine but I get this error when running it inside ccnet.

The application that runs before ncoverexplorer.console is ncover to generate the coverage.xml file and that completes just fine.

Any ideas?

Thanks.