readproperty error

I've defined a property like this:

Public Property Get VP_Data() As String()
VP_Data = myStrings
End Property

Public Property Let VP_Data(theData() As String)
ReDim Preserve myStrings(UBound(theData))
myStrings = theData
'Call copyArray(theData, myStrings)
PropertyChanged "VP_Data"
End Property

Now in the ReadProperties event I type like this:
Me.VP_Data = PropBag.ReadProperty("VP_Data") and get a
"Type mismatch: array or user-defined type expected" error. Why?
To save the property I use:
Call PropBag.WriteProperty("VP_Data", myStrings, "") and that seems to work..