Problem with dual channel mode

All kind time of days, the problem is that when running in dual channel mode the memory fails, any error occurs, throws a blue screen and so on. Configuration: core 2 quad q9550, 4 gb ddr2 (2x2gb), msi p43 neo, gtx 650 1gb, windows 7. The motherboard has 4 memory slots, if you insert the dies 1 and 2 slots everything is fine, 3 and 4 everything is good, everything goes smoothly, no bugs, crashes, etc, in such locations dies, the memory runs in single channel mode and everything is fine. The situation changes if these 2 dies are placed in slots 1 and 3 or 2 and 4, in such locations have problems. Dies are memory the same acceleration no no. There is a necessity in the work of dual-channel mode, so to go 2 more dice for 2 GB of the same manufacturer. Thanks in advance for your help.