Strange exception with ReportViewer control

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We're the ReportViewer Control in a .NET 2.0 winforms app.

Here's the call I'm making:

byte[] reportBytes = this.reportViewerInstallRpt.LocalReport.Render("PD F",
null, out mimeType, out encoding, out extension, out streamids, out warnings);

Here's the exception:
A call to PInvoke function
'Microsoft.ReportViewer.Common!Microsoft.Reporting Services.Rendering.ImageRenderer.CompositionPDF+Wi ndowsGDIWrapper::GetGlyphIndicesW'
has unbalanced the stack. This is likely because the managed PInvoke
signature does not match the unmanaged target signature. Check that the
calling convention and parameters of the PInvoke signature match the target
unmanaged signature.

The exception only happens intermittently on some machines, but always on
some other machines. This makes me think there is some kind of configuration
problem, perhaps. However, we are all using Visual Studio 2005 SP1 -- exact
same version of .NET framework and VS.

Any thoughts on why this is happening?