j.ramon,
Sorry that you are seeing this issue. I could not replicate the issue at my end on MyEclipse 10.7.1 with over 100 action classes.
1. Can you please update to 10.7.1 from the MyEclipse Configuration Center and then delete the contents of the .log file which is located at <workspace dir>/.metadata/.log, now try the ‘Export Image’ and copy paste the contents of the .log file here for us to investigate further?
2. Can you also try increasing the Xmx value in the myeclipse.ini file which is located in the MyEclipse installation folder and see if it helps?
3. If you are still seeing issues after increasing the -Xmx, please share your project details, like how many action classes are there , etc. along with the .log file contents.