fixed issue 1527 with smartgrid (again), thanks ato.steil

VERSION

@@ -1 +1 @@
-Version 2.5.1-stable+timestamp.2013.06.18.07.22.19
+Version 2.5.1-stable+timestamp.2013.06.18.07.44.05

gluon/sqlhtml.py

@@ -1959,7 +1959,7 @@ class SQLFORM(FORM):
                 tablenames += db._adapter.tables(join)
         tables = [db[tablename] for tablename in tablenames]
         if fields:
-            columns = copy.copy(fields)
+            columns = [f for f in fields if f.tablename in tablenames]
         else:
             fields = []
             columns = []