PartCover producing empty xml when upgrading applications to .Net 4.0

We have been running PartCover on applications, and they were producing xml reports just fine. However, we upgraded all our applications from .Net 3.5 to .Net 4.0, and now, PartCover just produces an empty XML file. I tried upgrading to latest NUnit and latest PartCover, but that did not help. Is there anything else I can do to try to resolve this issue? We've been using code coverage frequently as part of our process, and need to resolve.

This is the command:

"C:\Program Files (x86)\PartCover\PartCover .NET 4.0\PartCover.exe" --target "C:\Program Files (x86)\NUnit 2.5.10\bin\net-2.0\nunit-console-x86.exe" --target-args "{dll of app to coverr} /xml开发者_如何学Python=results1.xml /noshadow" --settings {xml file for settings} --output CoverageReport.xml