Andre,
I was able to "touch" all of the files, so it does not appear that any are locked. I then restarted the services on the host, and tried a delete again from datastore browser, but still no luck...same "cannot delete file" error. I tried each of the remaining files in the folder (as some I was able to delete earlier), and no luck. Here is what is left:
[root@lpesx2 backup]# ls -al
total 97231296
drwxr-xr-x 1 root root 1820 Jan 7 14:58 .
drwxr-xr-x 1 root root 3640 Jan 7 13:56 ..
-rw------- 1 root root 13589630976 Jan 7 14:58 vcenter-000001-delta.vmdk
-rw------- 1 root root 432 Jan 7 14:58 vcenter-000001.vmdk
-rw------- 1 root root 67194880 Jan 7 15:01 vcenter-000002-delta.vmdk
-rw-r--r-- 1 root root 0 Jan 7 14:58 vcenter-000002.delta.vmdk
-rw------- 1 root root 414 Jan 7 14:58 vcenter-000002.vmdk
-rw------- 1 root root 21474836480 Jan 7 14:57 vcenter_1-flat.vmdk
-rw------- 1 root root 581 Jan 7 14:57 vcenter_1.vmdk
-rw------- 1 root root 21474836480 Jan 7 14:57 vcenter_2-flat.vmdk
-rw------- 1 root root 581 Jan 7 14:57 vcenter_2.vmdk
-rw------- 1 root root 42949672960 Jan 7 14:57 vcenter-flat.vmdk
-rw------- 1 root root 577 Jan 7 14:57 vcenter.vmdk
[root@lpesx2 backup]#
Any thoughts on anything else to try?