How to resolve a "CompileXaml task could not be instantiated"... error?

[EDN Admin]

Hello everyone,
Im trying to build a solution from TFS. The solution is unable to build due to one of the projects. The project involved uses Silverlight 3 and the following error message is displayed in the Error List window:

Error 64 <span style="white-spacere
The "CompileXaml" task could not be instantiated from "Crogram Files (x86)MSBuildMicrosoftSilverlightv3.0Microsoft.Silverlight.Build.Tasks.dll". The security state of an AppDomain was modified by an AppDomainManager configured with the NoSecurityChanges
flag.<br/>
<br/>
Error 65 <span style="white-spacere
The "CompileXaml" task has been declared or used incorrectly, or failed during construction. Check the spelling of the task name and the assembly name.<br/>


Moreover, when I open Error64, VS opens the following file from path "Crogram Files (x86)MSBuildMicrosoftSilverlightv3.0Microsoft.Silverlight.Common.targets" highlight the following child element in the property group being an issue
ValidateXaml :

<span style="white-spacere <PropertyGroup><br/>
<span style="white-spacere <ValidateXaml Condition="$(ValidateXaml) == true</ValidateXaml><br/>
<span style="white-spacere ....<br/>
<span style="white-spacere </PropertyGroup>

VS states ValidateXaml is an invalid child element in namespace "http://schemas.microsoft.com/developer/msbuild/2003"

Ive been looking at different forums, trying to find an answer to this issue. Non of the other developers (in company) have had this issue and puzzled why Im facing such an issue.

Any ideas ?
<br/>

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