Ajax Update Progress Issue on back button iPad and iPhone safari

I have an ajax update progress panel in a page.

<asp:UpdateProgress ID="UpdateProgressIndicator" runat="server" DisplayAfter="100"><ProgressTemplate><div id="progressBackground"></div><div class="updateprogress"><font size="6">Loading...</font></div></ProgressTemplate></asp:UpdateProgress>

Following is the script that is executed on a page load

function showProcessing() {$("#UpdateProgressIndicator").show();
}

This works fine if I navigate to page by clicking on the required link.

If i click browser back button in safari (iPad), the page is stuck showing 'loading....' and background is disabled. I'm unable to do any action on the page after that.

Does anyone faced this issue?

Can anyone provide solution?

Thanks in advance.