Date: 9/11/2008 12:30 am EDT
Both acetone and naphtha will remove the glue without harming the tile. The tile is a high-quality porcelain and will not be effected by these chemicals.
Acetone and naphtha could however have an effect on this particular grout product as well as the plastic trays under the tile. Cleaning of surface glue should be controlled and deliberate and no damage should occur.
In my opinion the first attempt at cleaning the glue should be by using a razor-blade scraper. This will remove the bulk of the adhesive. Then if a noticeable residue remains the above mentioned chemicals could be used.