Crash when getting user's groups

[TobbeSweden]

Why does the following code crash sometimes when I run it?

code:
Name "EnumUsersGroups"

OutFile "EnumUsersGroups.exe"



!macro GetUserGroups SERVER_NAME USERNAME GROUP_ARRAY_NAME

    Push $R0

    Push $R1

    Push $R2

    Push $R3



    # NET_API_STATUS NetUserGetLocalGroups(

    #     __in   LPCWSTR servername,

    #     __in   LPCWSTR username,

    #     __in   DWORD level,

    #     __in   DWORD flags,

    #     __out  LPBYTE *bufptr,

    #     __in   DWORD prefmaxlen,

    #     __out  LPDWORD entriesread,

    #     __out  LPDWORD totalentries

    # );



    # $R0 buffer with an array of LOCALGROUP_USERS_INFO_0 structures

    # $R1 holds the number of entries processed

    System::Call 'netapi32::NetUserGetLocalGroups(w "${SERVER_NAME}", w "${USERNAME}", \

        i 0, i 0, *i .R0, i ${NSIS_MAX_STRLEN}, *i .R1, *i .R2) i .R3'

    StrCpy $R2 $R0 ; Needed to free the buffer later



    # check for error

    StrCmp $R3 0 +1 +2



    System::Call "*$R0(w.R3)"



    # Cleanup

    StrCmp $R2 0 +2

        System::Call 'netapi32.dll::NetApiBufferFree(i R2) i .R0'



    Pop $R3

    Pop $R2

    Pop $R1

    Pop $R0

!macroend



!define GetUserGroups "!insertmacro GetUserGroups"



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Page instfiles



Section ""

    ${GetUserGroups} "" "Tobbe" GroupArray

SectionEnd