Version: 1.5.5 (using KDE KDE 3.5.5) Installed from: Unspecified Linux OS: Linux Umbrello failed to load class, and sequence diagrams from the XMI file. It started to fail after doing undo while drawing the sequence diagram. Whenever, I start Umbrello with my xmi file it complains about "UMLRole::load: type not given or illegal".
Created attachment 18596 [details] XMI file after the undo operation
Fixed in current KDE SVN branches/KDE/3.5/kdesdk. I'm afraid your sequence diagram is lost (it's not in the XMI file.) Please use at least version 1.5.51 from sf.net - 1.5.5 had serious problems.