Your usage of Fractorium should be free of rendering errors and program crashes. However, there might be a bug in the particular version you are using so this section details how to proceed when problems occur.
The most severe situation is a program crash. In this case you will want to immediately recover what you were working on. Upon every completion of a render in the main window, the parameters of the flame being rendered are saved to a file named last.flame in the program folder (or ~/.config/fractorium on Linux). So before restarting, copy that file out to another location on disk, then restart Fractorium and load the file back in. Note that it’s very important to do this, otherwise restarting will just overwrite last.flame with the randomly generated flame that is created every time Fractorium starts and your previous data will be lost.
A less severe case is when the rendering process fails, but the overall program is fine. When this happens, the output will be blank and you will see an error in the status bar like so:
One common cause for this is setting the size and supersample to a value that requires an amount of memory greater than is available on your system. To find out the exact cause, see the text boxes in the Info | Bounds tab.
You can restart a railed render by switching the precision (toggle DP/SP) or switching the type (toggle CPU/CL). However, doing so is unlikely to help because failing in one case will likely fail in all cases. If you encounter this scenario, please submit a bug report. If the render keeps failing, you can get back to a stable state by loading a new flame.