my mistake or bug? Unity compiler error

Hey,

I've only been working with gui and very light networking in Photon.

I got this before, so I saved, shutdown unity and monodevelop and tried again, but when I reopened unity, it gave me some window about changing my layout back to the default for some reason. Then this error was in the console again.

I'm using the very latest 4.5 version.

Is this a bug to do with the release? Should I reinstall the version before?

 Internal compiler error. See the console log for more information. output was:
 Unhandled Exception: System.TypeLoadException: Could not load type 'System.Func`1' from assembly 'mscorlib, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e'.
   at (wrapper managed-to-native) System.Reflection.MonoMethodInfo:get_method_info (intptr,System.Reflection.MonoMethodInfo&)
   at System.Reflection.MonoMethodInfo.GetMethodInfo (IntPtr handle) [0x00000] in <filename unknown>:0 
   at System.Reflection.MonoMethodInfo.GetAttributes (IntPtr handle) [0x00000] in <filename unknown>:0 
   at System.Reflection.MonoMethod.get_Attributes () [0x00000] in <filename unknown>:0 
   at System.Reflection.MethodBase.get_IsVirtual () [0x00000] in <filename unknown>:0 
   at Mono.CSharp.MemberCache.AddMethods (BindingFlags bf, System.Type type) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.MemberCache.AddMethods (System.Type type) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.MemberCache..ctor (IMemberContainer container) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.TypeHandle..ctor (System.Type type) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.TypeHandle.GetTypeHandle (System.Type t) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.TypeHandle.GetMemberCache (System.Type t) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.TypeManager.MemberLookup_FindMembers (System.Type t, MemberTypes mt, BindingFlags bf, System.String name, System.Boolean& used_cache) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.TypeManager.RealMemberLookup (System.Type invocation_type, System.Type qualifier_type, System.Type queried_type, MemberTypes mt, BindingFlags original_bf, System.String name, IList almost_match) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.TypeManager.MemberLookup (System.Type invocation_type, System.Type qualifier_type, System.Type queried_type, MemberTypes mt, BindingFlags original_bf, System.String name, IList almost_match) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Expression.MemberLookup (Mono.CSharp.CompilerContext ctx, System.Type container_type, System.Type qualifier_type, System.Type queried_type, System.String name, MemberTypes mt, BindingFlags bf, Location loc) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Expression.MemberLookup (Mono.CSharp.CompilerContext ctx, System.Type container_type, System.Type qualifier_type, System.Type queried_type, System.String name, Location loc) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.MemberAccess.DoResolve (Mono.CSharp.ResolveContext ec, Mono.CSharp.Expression right_side) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.MemberAccess.DoResolve (Mono.CSharp.ResolveContext ec) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Expression.Resolve (Mono.CSharp.ResolveContext ec, ResolveFlags flags) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Invocation.DoResolve (Mono.CSharp.ResolveContext ec) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Expression.Resolve (Mono.CSharp.ResolveContext ec, ResolveFlags flags) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Expression.Resolve (Mono.CSharp.ResolveContext ec) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Return.DoResolve (Mono.CSharp.BlockContext ec) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.ExitStatement.Resolve (Mono.CSharp.BlockContext ec) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.Block.Resolve (Mono.CSharp.BlockContext ec) [0x00000] in <filename unknown>:0 
   at Mono.CSharp.ToplevelBlock.Resolve (Mono.CSharp.FlowBranching parent, Mono.CSharp.BlockContext rc, Mono.CSharp.ParametersCompiled ip, IMethodData md) [0x00000] in <filename unknown>:0