Something you should know: If you are using Windows 7 and get double accents when typing, you might have a serious problem, because it seems like this is a side effect of any activated keyloggers. While it’s nice that these cannot be active entirely unnoticed, it is annoying if you use a program that you want to log your keyboard actions.
In my case, the text expander FastFox was acting as a desired keylogger to supply shortcuts while I typed.
This notice showed up in a file with
__halt_compiler() occasionaly. It took me some time to get the problem… the error came only when I refreshed the page within short time, so after a while I suspected the opcode cache to be the problem. Actually it was related to APC and I found the following bug report:
Solution: Upgrade APC or just use other methods to store data than at the end of a PHP script 😉