I have a 1 1/2 Y/O Pentax K100D SLR. Often it will give me a "Battery Depleted" message and won't work. This happens with fresh batteries that I have metered so I know they are good. Any suggestions?

Seems to me this is not an uncommon problem... are you using alkaline or lithium batts?

Look here:
K100D battery life - PentaxForums.com (http://www.pentaxforums.com/forums/pentax-dslr-discussion/16175-k100d-battery-life.html)

And Here:
K100D - "Low-Battery" Problem - PentaxForums.com (http://www.pentaxforums.com/forums/pentax-dslr-discussion/2923-k100d-low-battery-problem.html)

Using Energizer Industrials (Alkaline I"m sure) but this is a very recent problem. I"vee shooting it for some time with no trouble with the same batteries.

Using Energizer Industrials (Alkaline I"m sure) but this is a very recent problem. I"vee shooting it for some time with no trouble with the same batteries.
This could be due to dirty/corroded battery contacts. Try cleaning the battery contacts in the camera using a clean pencil eraser. Hold the camera so that the eraser debris falls out of the battery compartment as you clean. Also clean the contacts on the battery. Clean both ends of the battery, and the contacts at both ends of the battery compartment. Depending on how the batteries fit in your camera one set of contacts may be in the battery compartment door.

If this doesn't fix the problem then try brand new batteries - there may be a problem with the set you have been using for a while.

If neither of these fix the problem, then the problem is internal in the camera. In that case, if the camera is still under warranty have it repaired (or replaced). If the camera is out of warranty usually the repair cost is greater than the value of the camera and you are better off putting the money towards a new camera.

Thank you. There might be a corrosion problem now that you mention it. This first started when on vacation at the beach in Florida last summer. I'll give it a try. Repairs must be outrageously expensive. It's about a $500.00 camera.

Thank you. There might be a corrosion problem now that you mention it. This first started when on vacation at the beach in Florida last summer. I'll give it a try. Repairs must be outrageously expensive. It's about a $500.00 camera.
If this started when you were at the beach, you may also have some success if you gently rub the contacts with some rubbing alcohol on a swab. Use a *barely* moist swab, and let the contacts dry for at least a few hours before you put batteries in and try again. If you have any salt residue on the contacts, this *may* help.

This could be due to dirty/corroded battery contacts. Try cleaning the battery contacts in the camera using a clean pencil eraser. Hold the camera so that the eraser debris falls out of the battery compartment as you clean. Also clean the contacts on the battery. Clean both ends of the battery, and the contacts at both ends of the battery compartment. Depending on how the batteries fit in your camera one set of contacts may be in the battery compartment door.

If this doesn't fix the problem then try brand new batteries - there may be a problem with the set you have been using for a while.

If neither of these fix the problem, then the problem is internal in the camera. In that case, if the camera is still under warranty have it repaired (or replaced). If the camera is out of warranty usually the repair cost is greater than the value of the camera and you are better off putting the money towards a new camera.
I misread what type of camera you have - since this is an SLR it is likely to be worth servicing. Often if you send it in for "clean and service" it will clear up problems of this type. I don't know what it will cost for your camera but for Canon DSLRs it usually runs ~$75-100, plus shipping.