Maybe you never have as BOINC is supposed to stop 1 or more tasks when exceeding user specified client permissions (which during user input and idle can differ), but not exceeding the tasks internal limits as set by the project and even then, if parts of the task can be offloaded to VM, BOINC will... slowing progress down as some seem to have observed during the CEP2 beta. If Lattice thus is hardwired to use 1.2Gb of RAM on 4 GB and OS use, you're probably lucky to get 3 going concurrently.

Fortunately, under Lunix Lucid Lynx, the swap inquiry suggests that this OS is a master at maximum utilization of RAM, even with 4 CEP2 concurrent barely seen differential between elapsed and cpu time when idle... and just 3 GB free.