Error "A specified parameter was not correct. spec.identity.userData.computerName" when creating a linked VM from a snapshot

The env is on vCenter 4.0 and ESX 4.0.

Here is part of customization code,

cSysPrep.setUserData(new CustomizationUserData());

cSysPrep.getUserData().setComputerName(new CustomizationFixedName());

((CustomizationFixedName) cSysPrep.getUserData().getComputerName()).setName(clonedVMName);

cSysPrep.getUserData().setFullName(winUserName);

cSysPrep.getUserData().setOrgName(winOrgName);

cSysPrep.getUserData().setProductId(winProductKey);

cSysPrep.setLicenseFilePrintData(new CustomizationLicenseFilePrintData());

cSysPrep.getLicenseFilePrintData().setAutoMode(CustomizationLicenseDataMode.perSeat);

cs.setIdentity(cSysPrep);

From trace log, I can tell the computer name was set properly. Any idea what could be wrong?

Also, I noticed when I try to clone VM from template through vCenter console, I got "Error reading customization specification". But the customization specification dialog does pop up after click ok on the error window. Not sure if it is related or not.