i know its not secure but there are some times i need wep…i can not find it anywhere! where is it? not in security profiles.
can i not access it with winbox?
normally i would not waste forum space, and i would search the manual but that function is not working
Under security profiles use mode static-keys-required.
if you are using R52 cards i suggest you to use WPA on virtual AP 
IMHO WEP is same as no encryption at all…
WEP security configuration example,
http://www.mikrotik.com/testdocs/ros/2.9/interface/wireless_content.php#4.13.21.6