This is a message to all users of the HP15CL. I have just seen messages in hpmuseum.org about a program error, whereby the whole program memory is erased, and in some cases, the calculator cannot get out of that state.
In general, this is a battery exhausted-related problem. The original hp15c had a warning when the battery level started to go below a threshold: a small star “*” would appear in the lower part of the screen. With the extremely low consumption of that model, that meant that you had at least one month to change the battery before the memory was erased.
Now, the HP15cLE works in a completely different manner. It uses the same firmware as the old one; but it runs on an emulation layer on an Atmel processor, of similar type to that of the HP30B. There have been very few modifications, so that the firmware can run in a completely different machine. However, there are a couple of bugs that have slipped in during the process. One of them is the odd working of the PSE function (which has been discussed here before); the other is the fact that the low battery indicator (our “*”) is not activated, and therefore there are brownouts before you can tell that something is happening. This means that you will lose your hard-entered programs; in my case, all of 222 program steps for the several programs I have entered. And you know that you will have to enter them again in 12 months from now (which is the typical battery life on normal conditions (meaning you don’t run calculation-intensive programs too often - like long loops, recursive algorithms, SOLVE procedures, etc.). This is quite upsetting for me! I have not entered again a program in one of my two units - the other is still updated.
If a firmware fix were to be developed, then it could be flashed on memory since the HP15CLE can be upgraded much the same way as the HP30b to be converted into a wp34s. And the memory needed is much smaller than that of the HP30B (which is around 128 kb), compared to around 10kb in this case. But please take a deep breath, and sit down - it’s not going to happen any time soon.