The problem with TortoiseSVN 1.5 icons, Opus and Windows XP has been solved and a fix will be included in the next Opus update. Edit: The update is out now.
(More detail here. TSVN 1.5 changed the way its icons work from the previous version, and not only that but they do their icons differently on Win2k, XP and Vista for some reason. That's why it took a while for us to spot, since it works fine on Vista.)
Edit: Didn't see your 2nd reply while writing mine. 