System low on memory error

Vegas Pro 9 used to be so dependable but lately having many problems. Sometimes not able to copy & paste from one instsnce to another but much more annoying is the " An error occured during an edit operation The system is low on memory you may be able to reduce memory usage by closing other applications. I have only 2 instances of Vegas open & hardly anything else open and memory usage shows about 47% on the task manager. This never was a problem before with as many as 8 instances of vegas open.

Ron