>Having tested additional combinations, it's now clear that the same 256 meg memory modules, when placed in either of two other 5000e's in our shop, work fine. And even more tests on the flakey machine using combos of less than 512 meg still run just fine. So it's not the memory per se. It must be something in the memory controller subsystem (on the mobo) or a memory address line problem on the CPU itself.
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>I use an offbeat technique to deal with flakey systems and unexpected breakdowns like this. It's similar to RAID. I call it "RAIN": Redundant Array of Inexpensive Notebooks. Periodically I make a bootable clone of my production hard drive using an Acronis product (EZ-Gig). Pretty fast. Takes about 35 minutes for a 30 gig hard drive over USB2. If I have a failure of either the production hard drive or the notebook itself, I'm back up in about 5 minutes plus (if it's a drive failure) needing only to do an incremental restore to the cloned HD for the piecemeal things backed up to a USB flash drive since the last clone operation.
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>Sure worked well this time. All I did was move the production hard drive into a backup notebook from my RAIN array of Inspiron 5000e's.
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>>My notebook computer (an old inspiron 5000e) suddenly has become unstable when I run it with 512 meg of memory. This is actually the max mem this model can handle. Sometimes won't boot. Sometimes boots up OK and then after an unpredictable time will either hard freeze or BSOD on me with a page-fault related "stop". etc. I've got several compatible memory modules of different capacities and have swapped them around. Oddly, the machine seems to run fine with less then 512 meg (i.e., 384, 256) regardless of which manufacturer's SODIMMs I use. But whenever I max out the memory with 2 x 256 SODIMMs, the system becomes unpredictably unstable. When I run the official (boot to DOS) Dell diagnostics with 512 meg, the diagnostics freeze up in progress rather than reporting an error. With less than 512 meg, I can't make it go wrong.
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>>Anybody else have a similar anecdote and a "most likely" cause? Thanks.

Are the BIOS versions the same on all 3 notebooks?