VS 2010 SP1 breaks add-in debugging targetting .NET Framework 2.0 rather than .NET Framework

I installed the Service Pack 1 (SP1) of Visual Studio 2010 last week and in a few hours I was already unhappy with it.

I use VS 2010 to develop my MZ-Tools add-in and since it targets VS 2005, VS 2008 and VS 2010 with a single binary add-in dll, the add-in project uses .NET Framework 2.0 and CLR 2.0 (the only one supported by VS 2005), not .NET Framework 4.0 with CLR 4.0. Soon after installing VS 2010 I noticed that breakpoints were not hit when debugging the add-in!

I created a new minimal add-in with the wizard and debugging worked. Then I tried to change the .NET Framework of the add-in project from 4.0 to 2.0, and the debugging stopped working. I reproduced it on two computers with SP1 applied to VS 2010, so I reported it to Microsoft:

VS 2010 SP1 breaks add-in debugging targetting .NET Framework 2.0 rather than .NET Framework 4.0
https://connect.microsoft.com/VisualStudio/feedback/details/650694/vs-2010-sp1-breaks-add-in-debugging-targetting-net-framework-2-0-rather-than-net-framework-4-0#details

And I am not the only one affected by this issue.

When I read the list of fixes of a service pack of any product, it seems
that it never fixes my bugs :-(. VS 2010 SP1 doesn’t fix a random crash that I experience deleting lines in VB.NET code, and due to the previous problem I can’t test if it fixes the Performance problem (100% CPU) for long time deattaching VS 2010 after debugging an add-in that happens with VS 2010 but not with VS 2008, and according to Microsoft, not with the next version of Visual Studio.

But at least I expect that a SP
doesn’t break something. This was not the case with VS 2010 SP1.