Wrong message "VMware Tools can be updated" for VM inside ESXi 4.1

Those VMware Tools in my guest OS keep on showing “VMware Tools can be updated” and the yellow exclamation.

Host OS is ESXi 4.1.0 build 348481

VMware Tools version is 8.4.8 build 491717

It’s not about the files with .001 extension as stated in the following article

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2001382

I have checked and there is no file with that extension.

I think the VMware Tools is unable to read or compare the correct numbers.  Or is there any other reason?