I was fooling around with the built-in assembler on my 49g+, and ran this program:

!ASM
LDR R0,[R1]
@

It reset and the memory was cleared, but it was suddenly very slow. I did a soft reset (ON+F3) to see if that would help, but now the screen is blank. I tried leaving the batteries (including the memory backup battery) out overnight, and that didn't work. I also tried following the instructions at http://www.hpcalc.org/hp49/pc/rom/ under "If it fails:" in case the firmware was erased, but no menu appeared.

More than a month later, I tried turning it on, and it appeared to work fine. I was able to perform several soft resets. Eventually, however (the next day) it started getting very slow again, and now the screen is blank again. What should I do?

To reproduce what I did (at your own risk!):

256 ATTACH "!ASM
LDR R0,[R1]
@" ASM EVAL

I do some HP programming, but I still know very little about SysRPL and ASM. I would almost think that what you described is some kind of hardware fault that just happened to crop up at about the time you ran that experimental code, since it seems unlikely that such a problem would persist after all the steps you took, unless some very unusual firmware corruption occurred.

You probably should look for some HP calc forums somewhere (I think I've seen a few) or the comp.sys.hp48 newsgroup, which still appears active, believe it or not (! I should subscribe to that!).

I'm bumping this because I think I may have found a solution. I've been able to get it working again briefly by leaving the batteries out for a while, but that had always been a temporary solution. I eventually decided to open it up to see if there was any obvious hardware damage. I opened it, no obvious damage. But apparently the simple act of opening the calculator itself did something that fixed the problem. Not only does it seem to be running noticeably faster, but the ON+F4 menu works as well; since I ran that code none of the menu options had done anything until now.

It's not immediately obvious how to open it, but easy when you know how. In case anyone else is having that problem, open the battery compartment, and you'll see these two light-grayish rivets. Take a screwdriver or a knife or something and pry at them until the wide part of the rivet comes off (just the part that sticks out past the black surface it's on) and then you'll be able to easily pry it open by sticking a screwdriver in the seam between the middle silver part and the black part on the back, when looking at it from the side. Then just snap the cover back on, and hopefully whatever happened to fix it for me will work for you as well.

EDIT: Never mind, it still seems to be intermittently having that problem 

Ciao,

it's instructive to read this topic:

50G - sporadic pauses - garbage collection ?
https://groups.google.com/forum/#!msg/comp.sys.hp48/SE7RfGC6uwk/y7KTrgY4zXIJ

You have to use FMEM by John H Meyers:

@ HP49/50 series only
\<< 5000. MAX :0:JUNK DUP PURGE MEM ROT -
IF DUP 0. > THEN MAKESTR SWAP STO
ELSE DROP2 END 0. DROP MEM \>> 'FMEM' STO
ex. 10000000 FMEM

===============================================================================================

also try installing latest version of the official firmware (ROM 2.15 http://www.hpcalc.org/details.php?id=7097), you will find instructions in the archive:

Fixing Strange Port2 Issues
An empty 50g Port2 will report 766KB in the filer. Occasionally, the 50g can have strange issues with
Port2 in which memory seems to have disappeared. Sometimes, when a third party program is deleted,
reinstalled or has a serious programming issue, the total amount of memory in Port2 is reduced and
seems to have disappeared. When everything in port 2 is deleted, the total memory has been reduced
to much smaller than 766KB.
To fix this problem, you can use the 2MB ROM image provided in this zip file. This ROM image will
completely overwrite the Flash Memory in the 50g and return it to original condition. Please note that
anything in Port2 will be deleted if you use this ROM image.
To use this ROM image, please unzip ‘2MB FIX’ and use the files inside for the upgrade procedure
previously explained. There is no need to re-flash using the regular ROM file again.