Problem after installing memory

I have a Mac Pro Quad-core Intel Xeon 3 GHz tower. I purchased it last year with 4 GB of memory, and yesterday I expanded it to 12 GB. I purchased my dimms from Ramjet and they are 100% Apple compliant, and compatible with Mac Pro.

After installing the new dimms, my Mac Pro recognizes the memory and all seems to be going well, but I have had sudden restarts happen 2 times so far. I will be working on After Effects (most of my work) and suddenly the screen goes black and restarts after a while. The first time it happened (yesterday after installing) the fans went nuts and I shut it down with the power button and after a while all came up fine, and I worked the rest of the afternoon. The last 2 times happened this morning. First it would not wake up so I had to restart. Then again I had a sudden restart, but this time without the fans going nuts.

I wonder if I should be putting the dimms in differently? Here is how I have them:

Originally I had a 1 GB dimm in the each of the top 2 slots of each riser, A & B. Now each riser has a 1 GB DIMM in slots 1 & 2, and a 2 GB DIMM in slots 3 & 4. Should I rearrange these? Although I seem to be able to work after a while, it seems that when it is still cold it runs a bit flaky. Any advice would be welcome. THANK YOU.

Miguel

Double check the ram specs and locations. As you know, they are very specific.
http://www.everymac.com/systems/apple/mac_pro/faq/mac-pro-how-to-upgrade-memory-what-type-ram.html

I do believe you have to or should install the 2GB DIMMs first.
If that doesn't work out, go back to the original RAM. If the original DIMMs work fine, the new stuff is most likely bad.

I have removed the original DIMMs and ran Hardware Test with just the new DIMMs, and all checked out fine. I will try running the MacPro for a day or 2 on just those DIMMs and if they do well I will install the 1 MB DIMMs in the lower slots and see what happens.

I'll keep you posted. THANKS.

i dont know about ramjet. But i have heard the ram from owc. Or go to macsales.com. Is some of the best ram you can get bro. Many of the guys in the magizines testing macs for render test us after effects,using ram from there.

All seems to be well. I called RAMJET, from whom I had purchased the memory, and they suggested I remove the original memory and run with JUST the new RAM. I did so, and did hardware diagnostics, and all seemed good. I ran the computer like that for a couple of days and then I put the original memory back in, but this time in the lower 2 slots instead of where they had been (at the top). Again I ran hardware diagnostics and checked temps and all passed. It has now been 2 weeks and all seems well. I think the computer likes the bigger dimms in the top slots. Thanks to all who helped!