Bizzare Excel Interop Behavior

[mwieder]

We have an Excel Automation Add-In that works fine for many of us. We
just installed at a client site and we are seeing very odd behavior
there. As an example, we have a wizard which outputs a formula into
the cell. When the wizard completes, only part of the formula is
making it into the cell - for example, we have Range.Formula =
"=MyFormula(1+2)" and what shows up in Excel is "=MyFormula" There
are other seemingly random exceptions thrown as well, such as
sometimes when we access Range.Value2, an exception is thrown. All of
this works fine on many other machines with the same version of Excel,
the same version of the .NET Framework and the same Interops. The
case with the formula rendering is really odd since it's breaking in
the middle of sending the data - half of the string got set for the
formula and then it just stops. Can anyone suggest what might be
going on in their environment, or some way to debug it? The debugger
is of no help since the problems are occurring after control leaves
the .NET code and before it completes in Excel.