I am using 2.0b4.
I have attached an example script so you can see what I'm getting at.
Firewall blocked it, added as code:
LangString InstallerRunning ${LANG_ENGLISH} "English: The installer is already running."
LangString InstallerRunning ${LANG_FRENCH} "French: The installer is already running."
LangString InstallerRunning ${LANG_GERMAN} "German: The installer is already running."
LangString InstallerRunning ${LANG_DUTCH} "Dutch: The installer is already running."
LangString InstallerRunning ${LANG_HEBREW} "Hebrew: The installer is already running."
Function .onInit
!insertmacro MUI_LANGDLL_DISPLAY
System::Call 'kernel32::CreateMutexA(i 0, i 0, t "LangString") i .r1 ?e'
Pop $R0
StrCmp $R0 0 +3
MessageBox MB_OK $(InstallerRunning)
Abort
FunctionEndedited by kichik, script attached below