Cannot open VSTO 2005/Excel 2003 customization files after migrated to VSTO2010 - visual-studio-2010

Question

I have a Excel Document level customization project that was build using VSTO 2005 that uses Excel 2003 template (xlt). Now I have migrated to VS2010 (.NET4) and Excel 2007 environment.
My application is a reporting tool that users can create Excel reports using the customization. So currently they have number of existing *.xls and *.xlsx reports.
My problem is after I have migrated my solution to VSTO2010, I cannot open previously created reports. It givesthe error,
Could not load file or assembly 'MyApp.BusinessAnalytics, Version=1.0.0.0,
Culture=neutral, PublicKeyToken=ff90f512e10aef0d' or one of its dependencies. This
assembly is built by a runtime newer than the currently loaded runtime and cannot be
loaded.
I am using MSI in order to install the application.
When I compared the application reports that created using VS2005 version and VS2010 version I have noticed the '_AssemblyName', '_AssemblyLocation' and 'Solution ID' is different in 2 versions. For an example, 2005/Excel 2003 version has * for _AssemblyName but 2010 has '4E3C66D5-58D4-491E-A7D4-64AF99AF6E8B'.
I have enabled the assembly binding log. and observed the assembly binding exception using fuslogvw.exe
The entry in Assembly binding log:
*** Assembly Binder Log Entry (8/3/2011 # 11:57:28 AM) ***
The operation failed.
Bind result: hr = 0x8013101b. No description available.
Assembly manager loaded from: C:\Windows\Microsoft.NET\Framework\v2.0.50727\mscorwks.dll
Running under executable C:\Program Files (x86)\Microsoft Office\Office12\EXCEL.EXE
--- A detailed error log follows.
=== Pre-bind state information ===
LOG: User = CORPNET\vohelk
LOG: DisplayName = Ifs.Application.BusinessAnalytics, Version=1.0.0.0, Culture=neutral, PublicKeyToken=ff90f512e10aef0d
(Fully-specified)
LOG: Appbase = file:///C:/Program Files (x86)/IFS Applications/IFS Business Analytics/
LOG: Initial PrivatePath = NULL
LOG: Dynamic Base = NULL
LOG: Cache Base = NULL
LOG: AppName = NULL
Calling assembly : (Unknown).
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Program Files (x86)\IFS Applications\IFS Business Analytics\Ifs.Application.BusinessAnalytics.dll.config
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework \v2.0.50727\config\machine.config.
LOG: Post-policy reference: Ifs.Application.BusinessAnalytics, Version=1.0.0.0, Culture=neutral, PublicKeyToken=ff90f512e10aef0d
LOG: GAC Lookup was unsuccessful.
LOG: Attempting download of new URL file:///C:/Program Files (x86)/IFS Applications/IFS Business Analytics/Ifs.Application.BusinessAnalytics.DLL.
LOG: Assembly download was successful. Attempting setup of file: C:\Program Files (x86)\IFS Applications\IFS Business Analytics\Ifs.Application.BusinessAnalytics.dll
LOG: Entering download cache setup phase.
ERR: Error extracting manifest import from file (hr = 0x8013101b).
ERR: Setup failed with hr = 0x8013101b.
ERR: Failed to complete setup of assembly (hr = 0x8013101b). Probing terminated.
Do you have any clue on this. Greatly appreciate your help regarding this.

Answer 1

Notice that in your fushion log the assembly manager is still from v2.0 (This is where the message comes from since it is trying to load a v4 assembly inside the v2 runtime)
Upgrading requires a bit more work than simply opening it in vs2010 especially if you move to framework V4. A quick workaround for you could also be to target framework 3.5 instead of 4
How and what you need to change depends on where you are coming from and what you are using. Have a look at these two msdn documents on upgrading and review those steps carefully for your scenerio. It's a bit of a read but I experienced it as pretty complete and useful.
Upgrading and Migrating Office Solutions
and
Migrating Office Solutions to the .NET Framework 4