Hi, I tried a small POC with the following code and the vertical scrollbar is showing in all browsers - IE, Chrome, FireFox, etc.
<asp:Panel ID="Panel1" runat="server" Height="100px" Width="250px" ScrollBars="Vertical">
<asp:CheckBoxList ID="CheckBoxList1" runat="server">
<asp:ListItem>Item-1</asp:ListItem>
<asp:ListItem>Item-2</asp:ListItem>
<asp:ListItem>Item-3</asp:ListItem>
<asp:ListItem>Item-4</asp:ListItem>
<asp:ListItem>Item-5</asp:ListItem>
<asp:ListItem>Item-6</asp:ListItem>
<asp:ListItem>Item-7</asp:ListItem>
<asp:ListItem>Item-8</asp:ListItem>
</asp:CheckBoxList>
</asp:Panel>
Can you try this and let us know your outcome?
- DD