Cell Comment Truncating String?

I form a string and put that string into a selected cell as a comment. Mostly it works fine but as the string gets over a certain length (255 characters?), the string gets "truncated" in that only the characters over that length get put into the comment.

Here's the code that I use:

Public Sub getBellTimes()
    Dim cmnt As Comment
    Dim sStr As String
    sStr = "Bell Schedule" + Chr(10) + "    AM" + Chr(10)

...code to further develope the sStr value...

    MsgBox sStr
    MsgBox Len(sStr)
    ActiveSheet.Range("hold").AddComment (sStr)
    Set cmnt = ActiveSheet.Range("hold").Comment
    With cmnt.Shape.TextFrame
        .Characters.Text = ""
        .AutoSize = True
        .Characters.Text = sStr
    End With
End Sub

The sStr variable is correctly formed (as seen with the msgBox) prior to the time that I try to put it into the comment.

Any ideas what I'm doing wrong?

TIA.

Bob