The SqueezeCenter software (presumably the database, but perhaps the scanner), erroneously reports multiple instances of the same artist when the artist contains an extended character found in a tag.

An example:

A single album by Michael Bublé containing 13 tracks (actual album name: "Call Me Irresponsible").  Ripped as a WAVE file with a RIFF tag containing the artist tag "IART Michael Bublé".

After SqueezeCenter does a complete rescan of the music database, browsing "Music Library > Artists > 'M' shows 13 entries for Michael Bublé, one for each track in the album.

Editing the RIFF tag to read Michael Buble (note last character changed) and then doing a rescan causes SqueezeCenter to correctly only list one entry for artist Michael Buble.

Repeatable with other extended characters, for example the band Sigur Rós.  (Again changing the tag to Sigur Ros cures the problem).