Some questions:
- Are only the context menu tools that disappear? The InfoTip and InfoEdit continue active?
- After disappear they randomly appear again or you always need to reinstall?
- When this happen what is show in the PDF-ShellTools preferences editor, the context menu tools are checked or unchecked?
If unchecked almost sure something is changing the registry keys, Windows itself or another application you have installed on these computers.
The keys involved, you can check them using the Windows registry key editor, are:
In the next key
HKEY_CLASSES_ROOT\.pdfcheck the default value, if Acrobat V7 installed you have "
AcroExch.Document "
If this is the case check if this key exist
HKEY_CLASSES_ROOT\AcroExch.Document.7\ShellEx\ContextMenuHandlers\{E3FD95C1-D5B1-4929-B0EC-C156318EDD8F}If yes check also if the control is registered:
HKEY_CLASSES_ROOT\CLSID\{E3FD95C1-D5B1-4929-B0EC-C156318EDD8F}Check also if the shell extension is approved. In this key
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Shell Extensions\Approvedwe need to have there the ShellTools context menu extension CLSID
{E3FD95C1-D5B1-4929-B0EC-C156318EDD8F}Something is different on these two computers, and from here is not very easy to debug the problem. If you have not understood something or if this is too complicated let me know and we can thing in another approach
You can use this tools to monitorize these keys
http://www.microsoft.com/technet/sysinternals/utilities/regmon.mspxor
http://www.microsoft.com/technet/sysinternals/utilities/processmonitor.mspx