"memory is full" "error code 23" "not enough memory to complete this operation"

[RDR]

You might consider a source-code control product to maintain backup copies of your VIs so you are not writing VIs over again.  There are some free SCC products available and some documentation to get you started is available here:

http://decibel.ni.com/content/docs/DOC-1681

Cheers!