LINGO’s solver ran out of virtual system memory.  LINGO’s solver accesses memory from the system heap.  Adding more memory to your machine may help. Note, also, that the memory allocated to LINGO’s model generator is not available to the solver.  Thus, if too much memory is allocated to the generator there may not be enough left over for the solver.  If you are using a Windows version of LINGO, see the Solver|Options command for information on adjusting the generator memory level, otherwise, refer to the SET command.