Strange behavior when expanding Disk

I had a case recently when I was expanding a data disk on a server from 250GB to 280GB. Operating system on the server was 2008. I did the same as I always do. Expanded the disk in Vmware first, then ran the diskpart extend command. Everything seemed as normal, until I checked the disk size in Explorer. WTF the disk was not expanded, but diskpart reported another size. I checked disk management console and it told me the same as diskpart. Okay….. Strange… So I checked the uptime for the server and it had not been booted for a while. I also tried to run diskpart, shrink querymax. This command reported me that there where not enough memory available to execute the command. So I booted the server. When the server was up again I tried the shrink querymax command again. It reported that I could shrink the volume with 3GB. So I shrinked the volume with 1GB and that run successful. Then i ran the extend command again and everything reported fine in disk management and explorer…… Strange….