If you have a copy of uifiles\default folder, for simple changes like no title bars in chat windows, and are crashing on login, the you need to copy your uilfiles again. EQUI_KeyRingWnd.xml in particular You can keep your modified EQUI_ChatContainerWindow.xml but make sure the only change is "<Style_Titlebar>false</Style_Titlebar>".
if the ui doesn't use a custom keyring window then it shouldn't be in the custom ui folder. delete it and let EQ pull from the default.