Vista - why doesn't System.Collections.SortedList work in PowerShell

I'm doing this in CTP2 and the properties don't return any results.

$a = new-object System.Collections.SortedList
$a.add((get-date),1)
$a.add([datetime]'12/31/2009',2)

gm -in $a
TypeName: System.Collections.SortedList

Name MemberType Definition
---- ---------- ----------
Add Method System.Void Add(Object key,
Object value)
Clear Method System.Void Clear()
Clone Method System.Object Clone()
Contains Method System.Boolean Contains(Object
key)
ContainsKey Method System.Boolean ContainsKey(Object
key)
ContainsValue Method System.Boolean
ContainsValue(Object value)
CopyTo Method System.Void CopyTo(Array array,
Int32 arrayIndex)
Equals Method System.Boolean Equals(Object obj)
GetByIndex Method System.Object GetByIndex(Int32
index)
GetEnumerator Method
System.Collections.IDictionaryEnumerator GetEnumerator()
GetHashCode Method System.Int32 GetHashCode()
GetKey Method System.Object GetKey(Int32 index)
GetKeyList Method System.Collections.IList
GetKeyList()
GetType Method System.Type GetType()
GetValueList Method System.Collections.IList
GetValueList()
IndexOfKey Method System.Int32 IndexOfKey(Object
key)
IndexOfValue Method System.Int32 IndexOfValue(Object
value)
Remove Method System.Void Remove(Object key)
RemoveAt Method System.Void RemoveAt(Int32 index)
SetByIndex Method System.Void SetByIndex(Int32
index, Object value)
ToString Method System.String ToString()
TrimToSize Method System.Void TrimToSize()
Item ParameterizedProperty System.Object Item(Object key)
{get;set;}
Capacity Property System.Int32 Capacity {get;set;}
Count Property System.Int32 Count {get;}
IsFixedSize Property System.Boolean IsFixedSize {get;}
IsReadOnly Property System.Boolean IsReadOnly {get;}
IsSynchronized Property System.Boolean IsSynchronized
{get;}
Keys Property System.Collections.ICollection
Keys {get;}
SyncRoot Property System.Object SyncRoot {get;}
Values Property System.Collections.ICollection
Values {get;}

gm -in $a.keys
Get-Member : No object has been specified to get-member.
At line:1 char:3
+ gm <<<< -in $a.keys

gm -in $a.count
Get-Member : No object has been specified to get-member.
At line:1 char:3
+ gm <<<< -in $a.count