If you update to the latest version in the store it should include all fixes for Unity 4.7. Import the latest version and install from the Welcome Window.
Not sure what version of Playmaker you're using now, but if it's a big jump and you want to minimize changes to your current project you could also edit the first few lines of PlayMakerWelcomeWindow.cs to read:
#if (UNITY_4_3 || UNITY_4_5 || UNITY_4_6 || UNITY_4_7 || UNITY_5_0)
#define UNITY_PRE_5_1
#endif
BTW, this happened because Unity decided to release Unity 4.7 with a new version define, even though it was just a collection of patches for Unity 4.6. Unity 4.7 was a surprise release, with no beta, and it broke a lot of assets on the store that assumed the Unity4.x updates were finished. But we got a fix into the store pretty quickly...