reverting previous patch, Anthony is right, the patch is not backward compatible

VERSION

@@ -1 +1 @@
-Version 2.4.6-stable+timestamp.2013.05.06.19.09.29
+Version 2.4.6-stable+timestamp.2013.05.06.19.49.05

gluon/sqlhtml.py

@@ -1456,8 +1456,9 @@ class SQLFORM(FORM):
                     if not f:
                         continue
                     else:
-                        ufolder = field.uploadfolder or current.request.folder
+                        f = os.path.join(
-                        f = os.path.join(ufolder, os.path.normpath(f))
+                            current.request.folder, 
+                            os.path.normpath(f))
                         source_file = open(f, 'rb')
                         original_filename = os.path.split(f)[1]
                 elif hasattr(f, 'file'):