(Qt 5.4.1) This application failed to start because it could not find or load the Qt platform plugin “xcb”

Question

I reinstalled my ubuntu 14.04 and Qt 5.4.1 and Qtcreator.

Qt 5.4.1 was built from source with \"-opensource -nomake-test -nomake-example\" configure options.

Answer 1

for anyone that hasn't found the solution yet and desperately looking for an answer, this is a copy of what @wardw commented on the currently top rated answer, which helped me resolve my underlying issue.

export QT_DEBUG_PLUGINS=1

put this either in your run configuration or on the console before running your project and it will print more information about what is wrong.