With SWV 6.1 we replaced the old zip library with Chilkat Compression and with the new zip library we now have new error codes for import and export. Those that are familiar with the SDK and coding will recognize some of these error codes--though some of the names have changed-- and so instead of getting the ominous Error Code 18 you will get one of the following:
An error 1009 can be caused because of a zip error or because SWV is trying to export to a vsa that already exists without passing in the overwrite flag (API and SWVcmd) while a 1060 error is you're trying to import a layer that already exists (same GUID). A 1010 and 1095 errors would be a zip error (not aware of any other instances where this would come up) and a 1011 error means you're trying to import in something that doesn't exist or isn't a VSA.
For SWVadmin and SWVcmd users you should get an error message telling you what the problem is. Something we're working on is better error messages returned to a SVSadmin or SVScmd user, we've got some that are very cryptic, which you should see with all new features and eventually all older features will have new messages written.
A few other new error codes are below, you may not hit these often.