I can't install or remove anything from Fast App Manager and x-terminal.
It say:

Help me!!!!!!!!!!

Edit the file:
/var/lib/dpkg/info/account-plugin-salut.postinst
and comment the line
/etc/init.d/avahi-daemon start

/var/lib/dpkg/info/account-plugin-salut.postinst
/var/lib/dpkg/info/account-plugin-salut.postinst: line 6: /etc/init.d/avahi-daemon: not found

/etc/init.d/avahi-daemon start
/bin/sh: /etc/init.d/avahi-daemon: not found

Nooo, i don't want to flash.

No! Don't execute! Edit the file!
Don't worry.
Sorry, I explained wrong. And please, sorry about my poor English.
You can use nano, vim, leafpad... to edit the file.
And then, put "#" in the line etc/init.d/avahi-daemon start to comment it...

Successful!!
Thank you very much.

bro can u explain code in detail !??
my terminal says
dpkg not found !!!! :-(

i mean step by step

Yup, dpkg needs to be run as superuser in order to be useful. The only thing it will do as normal user is display help (--help).
To overcome this:

1. Open the terminal (called X Term in programme menu)
2. Type sudo gainroot
- you are now superuser and can quite easily trash your device!
- this state is limited to the terminal and will end when you close the terminal (don't worry, it's not like being windows administrator!).

People argue over whether nano or vi is the best - they're in line text editors, run from the terminal.
Although vi & nano are possible options, it's actually easier to use leafpad or a stand alone editor on the N900.

To edit an ascii (plain text) file you probably do need to terminal to start with...
1. a. Open the terminal (called X Term in programme menu)
2. a. Type sudo gainroot
3. a. Type leafpad <file-path>

1. b. Open Filebox
2. b. Navigate to desired folder
3. b. From hover menu, select "Edit" for desired file.
4. Make the edits.
5. Save & close.

Both methods, a and b, assume rootsh and leafpad are installed.
Method (b) assumes Filebox is installed as well, and Leafpad is its text-editor.

As per instructions above...
In case you need to install rootsh, Filebox or leafpad...
If the application manager is all frozen up when trying to downlad repository data etc, turn off all internet connections and transfer the deb files to the device via your pc with your device in usb mass storage mode. If you double click on a deb file in the built in file manager, the application manager will handle the installation.

but still my problem is not solved!!!!!

my problems:
1) while doing apt-get autoremove
it gives error " could not exec dpkg"

2) am not able to install any application through app manager or fam or x-terminal

3) when i tried "apt-get install dpkg"
it says cant install!!!!