To fix edit the file \"/home/root/usr/lib/ipkg/status\", at the bottom remove the failed ipkgs, save and exit. As least this is how I do it with Cacko 1.21 ROM on my c860. I suspect other Sharp ROMs are the same.
You probably got the error when trying to install an \'ar\' formatted ipkg. Some ROMs support the ar format other do not. There are other reasons for failure but the \'ar\' formatted packages I believe is the #1 cause.
If you cannot install ar formatted ipks then use ar x to extract and tar zcvf to recreate, then try to install.