ViewMail install error

I'm wondering if anyone has run into a problem where Cisco ViewMail 4.03b software does not install on a Windows 2000 OS with Office 2003. All patches have been applied for both the OS and Office. There is a weird installation error in the log: MSI (c) (F8:28): Doing action: OutlookVersionError Action start
> 12:36:42: OutlookVersionError
>> Property(C): CanNotInstallOnThisMachine = can not be installed on this
> machine
> Property(C): Win98MERpcDllAbortMsgRequiredText = The minimum required
> version of "rpcltscm.dll" is 4.71.3400.0 for installation to proceed.
> Please consult your system administrator or visit
> http://www.microsoft.com for the proper hotfix

We are not installing ViewMail on a Windows 98 computer, so I don't understand why we get this error. I am looking for the latest Rpcltscm.dll file, but haven't found it yet. Any suggestions