Sorry - image support in DOSBox is readonly. Meant for stuff like CD's.

No, floppy and hd images should be fully writeable,
unless i'm missing something here.

Can you copy files TO the floppy image (after img'mounting
with -t floppy as you did) ?

Well I mounted my hardrive as another drive (b:) and it was possible to copy a file from b: to a: (a: is where i have imgmount my img file). Though, still it is not possible to edit anything on a: even the file I copied.

How do you edit? Maybe try a different editor as well.

edit.com
It is somekind of dos-boot diskette with edit.com and some turbo c compilers. Any suggestion for editors? My mind is out of ideas

Dunno, maybe look through some shareware archives. Maybe try the
edit/qbasic from dos6.
But i don't see why your edit.com shouldn't work, maybe somebody else
can verify this. What happens if you save? (error message?)

"edit was unable to access the file 'a:\logfile.txt' ----> this is the exact message.
The funny thing is that I quit edit without saving the changes, but the file no longer exists. It has been deleted and sure not by me..

But edit works fine on regular mounted drives?

Yes. In fact i installed a virtual floppy and now mount the same img file to the virtual floppy and then mount it to dosbox and works fine.
I tried even to deploy the img file to a diskette and mount the diskette to DosBox and it also worked fine.

Is the read-only attribute set on the IMG file itself? (This is quite likely if the IMG file used to be on a CD-ROM.) Or perhaps you are running DOSBox as a user that does not have write-priviledges for the IMG file?

None of the above. I am the administrator and there is no write protection for the IMG file