Hi Mark, there is also a slight chance that you may have applied the solution to quickly after painting.
Though the finished surface is dry to touch, does not mean the paint has "cured " underneath.
Even though applying a protective clear coat is a good safety precaution, the decal setting solution should not have eaten through the paint regardless of a protective layer.

As matter of fact, I don't apply protective clear coats until the very last step ( unless using pastels ) .

It is also recommended that when using water-slide decals that a "gloss coat " should be first applied to the area where the decal will be placed. Then you will need to dull coat after that has dried.
I myself prefer "dry tranfers" to avoid this surface prep.

- ralph