Accordion's First Pane Flashes On Partial Postback - asp.net

Question

I'm using an ASP.NET Accordion control with lots of panes for a data entry form. Within several of the panes are some UpdatePanels, so that some controls within those panels can be enabled or disabled to prevent users from entering values into fields which are precluded by values they've entered elsewhere.
It all works fine, but for some reason, on about half of the occasions where an UpdatePanel postback is triggered (by a specified AsyncPostBack Trigger), the first pane of the Accordion momentarily expands and collapses. This gives that horrible 'flashing' experience you get when a page does a full postback, which is exactly what I'm trying to avoid by using UpdatePanels.
The problem doesn't seem to relate to the contents of the first pane - I tried completely deleting the first pane, so that the second pane became the first, and the same thing happens.
Anybody got any ideas why this is happening and how to fix it?
UPDATED WITH CODE
This is an example of one of the panels. Don't be too offended by the use of a table - it's an actual table, I'm not just using it for layout purposes!
<tr class="grouprow">
<td>Transportation</td>
<td><asp:RadioButtonList ID="rblTransportation" runat="server" RepeatDirection="Horizontal" SelectedValue='<%# Bind("AdmissionTransportation")%>' AutoPostBack="true"
OnSelectedIndexChanged="rblTransportation_SelectedIndexChanged" >
<asp:ListItem Text="Unknown" Value="" />
<asp:ListItem Text="Yes" Value="True" />
<asp:ListItem Text="No" Value="False" />
</asp:RadioButtonList></td><td></td>
</tr>
<tr class="grouprow">
<td>Transportation Duration</td>
<td><asp:UpdatePanel ID="updTransportationHours" runat="server" UpdateMode="Conditional">
<Triggers>
<asp:AsyncPostBackTrigger ControlID="rblTransportation" EventName="selectedindexchanged" />
</Triggers>
<ContentTemplate>
<asp:TextBox ID="txtTransportationHours" runat="server" Text='<%# Bind("AdmissionTransportationHours")%>' CssClass="tinytextbox" />
<label class="unit">Hours</label>
<asp:RegularExpressionValidator ID="revTransportationHours" runat="server" ControlToValidate="txtTransportationHours" ValidationExpression="\d{1,3}(\.\d{1,2})?"
ValidationGroup="Past30Days" ErrorMessage="Invalid format for Transporation Duration. Please enter in format 'xxx.xx', e.g. '3.25'" Display="Dynamic"
CssClass="error" >*</asp:RegularExpressionValidator>
<asp:RangeValidator ID="rvTransportationDuration" runat="server" ControlToValidate="txtTransportationHours" CssClass="error" ValidationGroup="Past30Days" type="Double"
ErrorMessage="The Transportation Duration cannot be more than 100" MinimumValue="0" MaximumValue="100" >*</asp:RangeValidator>
</ContentTemplate>
</asp:UpdatePanel></td><td></td>
</tr>

Answer 1

I believe you need your rblTransportation RadioButtonList wrapped in an UpdatePanel as well.
Since that control isn't in an UpdatePanel, it causes a full postback.

Answer 2

The answer is gloriously simple, though I'm too tired to figure out why it works just now. I simply need to set ClientIDMode = AutoID on the RadioButtonLists and CheckBoxLists and they now trigger an asynchronous postback rather than a full one. They don't need to be within their own UpdatePanels either.
I got the answer from this SO question.

Answer 3

Can you try <asp:blablacontrol style="Display:none;"> </asp:control>
modalpanels has same problem and this codes solved my problem