In PL5, you could create signatures with special characters. I signed for example with my email address. Impossible to enter the @ in PL6 signatures. 
Using the old presets even makes PL6 crash. I had to delete the presets created under PL5, and recreate signatures with only alphanumeric characters.
Dom…
Works fine for me. Are you using PL6 on Windows or Mac? Is your PL6 up-to-date? Also your video drivers and other device drivers? (The initial release of PhotoLab 6 did have some problems with Instant Watermarking, including not being able to use presets from PL5. These were fixed.)