In some instances, using non-standard iSCSI IQN naming can cause connecton problems.

For example you may see an error similar to:
(From Xen): 'Error connecting, target not found, check user name and password.'
Even though no username or password is required.

If the target name has been changed from the default standard of 'iqn.YYYY-MM:<hostname>.target0' you may see the problem mentioned above.
Always use the standard naming convention and only change the last portion (target0) if needed.
Depending on the version of Xen or VMware, this may or may not be required. It is best to always use the above standards.