The string are UIDs (unique IDentifier) that are used for accounts. If they ar./..e not showing the true name on the dialog, this is due to the link in AD not being there. Were the account migrated? Were they left over from the previous environment? ie, assigned to something, but the actual account wasn't there? this happens alot. Ussually, you can simple delete the entity, and this will make it look better.
As to the cause, that is more complex, as without the AD link to the account name, it's hard to back track it.
As to your folders, can you explain the config so it's a little more clear?