It seems that the bookmarklets don't work all the time. Specifically, if the URL in the address bar is a picture (perhaps all non-html media, I haven't played with it that much) bookmarklets in your tool bar don't work.
To reproduce:
Create a bookmarklet, say this "Up" bookmarklet here:
javascript
:if%20(location.pathname%20==%20%22/%22);%20else%20if%20(location.pathname.charAt(loca tion.pathname.length-1)%20==%20%22/%22)%20location%20=%20%22..%22;%20else%20location% 20=%20%22.%22;%20void%200
(Note, The forum software is broken, and won't insert the URL unmolested. You'll have to create it yourself.)
Load a picture in the browser, say this one:
http://darkstar.frop.org/~zwhite/pics/egeria.jpg
Click the bookmarklet. Either OmniWeb will attempt to visit the "address" of the bookmarklet, in which case you get an error page, or nothing will happen. I haven't been able to determine when or why each case occurs yet. In either case, this is not expected behavior.