Using slippy-map data overlay, can't select items in forest area
A region I've been working on has recently been covered by a mass-import of land-use (forest) data. Now, when I'm using the slippy-map data overlay, I can't select any of the ways that are now buried under the forest area (actually, "any" is not true, a few can be selected but it's not clear which ones); the entire forest area gets selected instead. Can anybody suggest how I might fix this? I've tried searching the wiki for stuff like z-ordering, but have come up with nothing useful.
The region in question is http://www.openstreetmap.org/?lat=41.528812&lon=1.2315&zoom=18 . I haven't I've looked at any other regions.
similar regions, where details have been covered by land-use areas; some of them seem to have the same problem, others have not.
Thanks a lot.