I'm running Ubuntu 14.04 LTS on a Dell Latitude E7450, with TeXstudio 2.6.6. I've been having GUI problems with TeXstudio since the automatic updates of the last few weeks (i.e. Oct./Nov. 2015). When I start TeXstudio, the GUI is almost completely gone: only part of the "+"-button for starting a new file appears, the rest of the window is grey. When I click it, a white rectangle appears, but no new buttons. When I open a text in TeXstudio, it does appear, but without scrollbars or buttons. Dragging with the mouse to select text results in selecting text a couple of lines away from my cursor. Logging out and in solves the problem, but it costs a lot of time to start everything up again, which naturally is destructive to my workflow. The problem seems to appear at random, but always while starting TeXstudio. Here a screenshot of the TeXstudio GUI after creating a new document and resizing (the latter creating the many horizontal lines).
A problem that might be related is that the text of context menu items disappears in TeXstudio, as well as in Dolphin. This problem has occurred since the same time, is either there or not at startup of the appliactions. See a screenshot here. Only the item which has the cursor over it, and sometimes the one over which the cursor has last hovered, are displayed. It is also solved by a login-logout.
Thanks a lot for any help.