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We have also learned that older versions of ag can cause the X11 server to hang (when opening up multiple windows quickly, like when opening an optimization?). Type ag-devel to pick up a new version that won't hang the X server.
At some point ag-devel stopped working as well. At that point we upgraded Jun to the latest Xquartz and it started functioning again.
When aleksandra upgraded snow-leopard to lion, several X applications stopped working. She manually deleted them ("drag to trash") and reinstalled.
applications ("drag to trash") and re-installed.