You cannot allocate more memory than your computer has available when openLCA starts. The allocated memory is entered into an openLCA.ini file which is basically a text file. It is in the same folder as openLCA.exe. Try to find it, open it, and in this file, search for
12345 is the allocated memory in MB (hence "M"), so here 12.345 MB, and in your case numbers will be different. Change this to an amount feasible for your computer, then save and restart openLCA.