I use WinEdt build 20131031 (v. 8.1) - 64-bit on a Windows 7 (64 bit) machine. My active strings are not working. I tried a lot, e.g., "Load Script" in the Options Interface (under Delimiters, Active Strings, Abbreviations... -> Active Strings).
For example, I would like to have the typical \ref{} active string (such that the labels given in the main file pop-up after typing in \ref{}). It does not work (by contrast to WinEdt 5 or so). Now it becomes really weird: I have created my own active strings and put them into a file called myActiveStrings.ini which is located in %b\ConfigEx\. In ActiveStrings.ini (i.e., the active strings file that comes with WinEdt) I inserted %INCLUDE="ConfigEx\myActiveStrings.ini". Now, my OWN active strings work, but not the active strings in ActiveStrings.ini!
Help...! ;-)