First, false positives happen all the time. Next, over-zealous AV products are quite common. AV software classifies malware a lot of different ways, and it's an imperfect science. When they don't have specific information on a specific piece of code, they make heuristic guesses based on the code signatures they detect. Problem is, those code signatures can be used in a lot of legitimate ways. Without any database knowledge about the code telling them otherwise, they will often err on the side of caution (or stupidity) and flag such as malware. I write software for a living, and have had my own code flagged on a number of occasions. EXE packers and code encryptors, for instance, commonly generate false hits.
If you ever have a question about a specific file or files, and aren't sure whether the problem might be your AV product, the best options are first to evaluate the situation with common sense: why would a (presumably, I don't know anything about PPN) legit poker site infect their users with malware? It makes no sense. And if it were an accident, it would have been caught and rectified quickly.
Also, use other resources to double-check. My suggestion is
VirusTotal, which is a free service that will take your uploaded files and run it through ALL the major AV products, including many you've never heard of, and give you a report of what each one finds.
