There are two issues at play here - the user account with permissions to the library and the user account that your local cache is tied to. I'm guessing that most people have Creo configured to have the local cache created based on local computer login name. Logging into Creo and the associated embedded browser with a different username than what the local cache is expecting can cause cache corruption. If your local cache is setup this way, then it's best to log onto both the local computer and Creo as the library user.
The alternative (as you mentioned) is to either have the admin manually move the library files after you check in somewhere else or temporairly add your account to the library creators group (or whatever it's named) long enough for you to be able to check in the files on your own. Both of these are very easy for an administrator to do. Around here I normally add someone to the creators group long enough to get their data checked in and then remove their permissions.
I imagine if you really wanted to you could create a workflow where someone could check new library parts into a central location and then as part of the approval process have the workflow automatically move them to their final resting place upon approval.
