Frequently on systems that are booting from usb and do not have scratchconfig space configured or even that are booting from a disk with insufficient free space the command to collect data using the vCenter server of vSphere client will fail with a general system error. You will need to collect the data manually using the steps in the document below. You can use your vsphere client datastore browser to upload the data to your desktop if you place it on a datastore. If it is on a local disk or boots from san then you will need to use a program such as winscp to copy the .tgz file off in order to upload to support.
How to manually collect VMware ESX/ESXi data using the vm-support -w command