If SmartGit, SmartSVN or SmartSynchronize crashes for you on dialogs where (on other platforms) comboboxes are visible, please check whether the oxygen-gtk style is selected. It is reported to be extremely buggy and better should be replaced with either Adwaita or Clearlooks-Phenix:
- Open the System Settings
- Select the Application Appearance
- On the GTK+ Appearance page select, e.g. Adwaita
Please also check out javaclipse.blogspot.de/2015/06/mars-on-linux.html for alternative hints.