I remember having that same problem. The wizzrobe will never spawn there on the newer versions of 2.5. You'll have to find an older version of 2.5 and copy your sav file onto that one.
Which older version would you recommend?
I use 2.5 RC3, to i guess i should downgrade to 2.5RC2 or 1? or is there a specific build i need to go down to?