Mixing /clr and /EHs
In VC++.NET 7.0 and 7.1, you can compile managed code (/clr) with both the synchronous (/EHs) and async (/EHa) exception models. However, in all cases, it's always better to use /EHa instead because of the way the CLR translates exceptions at managed/unmanaged boundaries.

In fact, in VC++ 2005 (aka whidbey), mixing /clr (any of it's variants) and /EHs will not be possible; the compiler will require you to especify /EHa instead. Given this, it is a good time to ensure your applications are being compiled now with the appropiate combinations of switches