CF9.01 AJAX errors

We are trying to upgrade from CF8 to CF9 but some of our AJAX related code is failing intermittently. This code works fine in CF8.  Any insights would be greatly appreciated.

Old Environment

CF8.01 (including cumulative hotfix 4)

Windows 2003 R2 Standard SP2

SunONE Web Server 6.1.9

New Environment

CF9.01 (including cumulative hotfix 2)

Windows 2008 R2 Standard SP1

SunONE Web Server 7.0.13

We have a simple tabbed interface using cflayout and cflayoutarea.  Here is an example of the code.  All the files are in the same directory.  The code and directory structure have not changed.  I also see intermittent errors on cfselect AJAX binding; the cfselect will work once, then fail, then work, then fail, etc.

<cflayout type="tab" name="mainTab">

    <cflayoutarea title="Summary" name="tab1" source="PackageFormTabSummary.cfm" refreshOnActivate="true" />

    <cflayoutarea title="Contract" name="tab2" source="PackageFormTabContract.cfm" refreshOnActivate="true" />

    <cflayoutarea title="Machine" name="tab3" source="PackageFormTabMachine.cfm" refreshOnActivate="true" />

    <cflayoutarea title="Finance" name="tab4" source="PackageFormTabFinance.cfm" refreshOnActivate="true" />

    <cflayoutarea title="Parts" name="tab5" source="PackageFormTabPart.cfm" refreshOnActivate="true" />

</cflayout>

This is the error we see:

"Server Error

This server has encountered an internal error which prevents it from fulfilling your request. The most likely cause is a misconfiguration. Please ask the administrator to look for messages in the server's error log."

But it doesn't happen every time.  For example, we might see the following results:

Page Test #1: tabs 1,3,5 error

Page Test #2: tabs 1,2,4 error

Page Test #3: tabs 2,3,4 error

Page Test #4: tabs 1,2,3,4,5 error

Page Test #5: tabs 3,4,5 error

FireBug shows "200 OK" for the tabs that succeed and "500 Server Error" for the tabs that fail.