Problem with Deserialization

Hi,

I am creating a excel plugin, where i have to create a Tree on Excel
worksheet, so while saving i also want to save the tree in serialized form as
a custom property of worksheet.

Hence, i am using a BinaryFormatter, which serializes the Tree object and
saves the result in form of a string and attach it to a cutom property of
sheet.This Works fine.

[Tree is comprised of nodes(NODE class, also marked serializable)], While
De-serializing, it works fine , untill number of nodes in tree exceeds 24.So
when N(nodes) 24 , i get two types of exceptions, any one of them randomly.

1)
at System.Runtime.Serialization.ObjectManager.Registe rObject(Object obj,
Int64 objectID, SerializationInfo info, Int64 idOfContainingObj, MemberInfo
member, Int32[] arrayIndex)
at
System.Runtime.Serialization.Formatters.Binary.Obj ectReader.RegisterObject(Object obj, ParseRecord pr, ParseRecord objectPr, Boolean bIsString)
at
System.Runtime.Serialization.Formatters.Binary.Obj ectReader.ParseObjectEnd(ParseRecord pr)
at
System.Runtime.Serialization.Formatters.Binary.Obj ectReader.Parse(ParseRecord
pr)
at System.Runtime.Serialization.Formatters.Binary.__B inaryParser.Run()
at
System.Runtime.Serialization.Formatters.Binary.Obj ectReader.Deserialize(HeaderHandler
handler, __BinaryParser serParser, Boolean fCheck, Boolean isCrossAppDomain,
IMethodCallMessage methodCallMessage)
at
System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter.Deserialize(Stream
serializationStream, HeaderHandler handler, Boolean fCheck, Boolean
isCrossAppDomain, IMethodCallMessage methodCallMessage)
at
System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter.Deserialize(Stream serializationStream)
at ProbTreeDemo.Connect.WorkBookOpened(Workbook myWorkBook) in
C:\Docs\Visual Studio 2005\Projects\ProbTreeDemo\Connect.cs:line 286

Error Message :- An object cannot be registered twice.

2)
at System.RuntimeType.CheckValue(Object value, Binder binder, CultureInfo
culture, BindingFlags invokeAttr)
at System.Reflection.RtFieldInfo.InternalSetValue(Obj ect obj, Object
value, BindingFlags invokeAttr, Binder binder, CultureInfo culture, Boolean
doVisibilityCheck, Boolean doCheckConsistency)
at
System.Runtime.Serialization.FormatterServices.Ser ializationSetValue(MemberInfo fi, Object target, Object value)
at
System.Runtime.Serialization.FormatterServices.Pop ulateObjectMembers(Object
obj, MemberInfo[] members, Object[] data)
at
System.Runtime.Serialization.Formatters.Binary.Rea dObjectInfo.PopulateObjectMembers(Object obj, Object[] memberData)
at
System.Runtime.Serialization.Formatters.Binary.Obj ectReader.ParseObjectEnd(ParseRecord pr)
at
System.Runtime.Serialization.Formatters.Binary.Obj ectReader.Parse(ParseRecord
pr)
at System.Runtime.Serialization.Formatters.Binary.__B inaryParser.Run()
at
System.Runtime.Serialization.Formatters.Binary.Obj ectReader.Deserialize(HeaderHandler
handler, __BinaryParser serParser, Boolean fCheck, Boolean isCrossAppDomain,
IMethodCallMessage methodCallMessage)
at
System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter.Deserialize(Stream
serializationStream, HeaderHandler handler, Boolean fCheck, Boolean
isCrossAppDomain, IMethodCallMessage methodCallMessage)
at
System.Runtime.Serialization.Formatters.Binary.Bin aryFormatter.Deserialize(Stream serializationStream)
at ProbTreeDemo.Connect.WorkBookOpened(Workbook myWorkBook) in
C:\Docs\Visual Studio 2005\Projects\ProbTreeDemo\Connect.cs:line 286

Error Message:- Object of type 'ProbTreeDemo.TreeStructure.Node' cannot be
converted to type 'System.Object[]'.

Source is botth cases is "mscorlib".
Code at line 286:- Tree temp =(Tree)bformatter.Deserialize(stream);