Hello friends, this is my first thread, sorry for ignorance, I researched a lot here in the forum and did not find the solution. I've had my n9 for 6 years, and every once in a while I flash him (flasher -f -F DFL61_HARMATTAN_40.2012.21-3_PR_LEGACY_001-OEM1-958_ARM.bin -F DFL61_HARMATTAN_40.2012.13-7.LTA_EMMC_LTA.bin --erase-user-data). But since the last flash last week, I can not install some applications. Apparently the error is 255 (setup interrupted)Operation failed: E: sub-process Usr/bin/dpkg returned an error code (255). I must have flashed some 50 times my n9 during this 6 years and always managed to install my apps. But this time around 30 percent of the apps I want to install is giving this error. Do you have any idea what's wrong?

Maybe some kind of memory error try to zeroise device(note it takes about an hour or so)

refer to here: http://talk.maemo.org/showthread.php?t=82693

side note(s):
DFL61_HARMATTAN_40.2012.21-3_PR_LEGACY_001-OEM1-958_ARM.bin is your main.bin

and

DFL61_HARMATTAN_40.2012.13-7.LTA_EMMC_LTA.bin is your emmc.bin

(i think you already know this but its better if you name them that way (i did and it made flashing easier to type in))

Have you tried through the terminal?
I have the same error & this terminal error:
Aegis rejecting [filename]: package '[package name]' origin cannot be determined -- signature check failed
As I'm new to the phone, I haven't yet figured out how to do the solution steps (eg. how to refresh packages list).

Hello friends. I think I found the solution after searching here in the forum. Has to do with the validity of application certificates. Many that I usually install are outdated certificates. Using aegis hack(http://talk.maemo.org/showthread.php?t=90750) solve the problem. But it has a simpler way that also solves by simply changing the phone date to a few years ago. An example application that is impossible to install is the Reboot (https://openrepos.net/content/kamengatalica/reboot). Test with today's date(can not install without the aegis hack) and then try to put the year 2015 that will work(even without installing the aegis hack)

Thanks. It solved my problem !!