You'll need to enable Pango on Firefox and Mozilla. Fortunately, Ubuntu comes with firefox compiled with Pango support, but Pango support is disabled by default for locale other than Bengali, Gujarathi, Hindi, Kannada, Malayalam, Marathi, Nepal, Tamil and Telugu.

Open /usr/bin/firefox in a text editor

$sudo nano /usr/bin/firefox


and look for these lines

if [ "x${MOZ_DISABLE_PANGO}" = x ]; then
if egrep '^(bn|gu|hi|kn|ml|mr|ne|pa|ta|te)_' \
/var/lib/locales/supported.d/*[^~] >/dev/null 2>&1; then
MOZ_DISABLE_PANGO=0
else
MOZ_DISABLE_PANGO=1
fi
export MOZ_DISABLE_PANGO
fi
if [ "x${MOZ_DISABLE_PANGO}" = x0 ]; then
unset MOZ_DISABLE_PANGO
fi


Edit the above lines to either set disable flag to 0 for all locale or just add your current locale to the regex on the if egrep '^(bn... line.

*******

There's a known issue with SCIM-m17n on 6.06. Due to version mismatch between m17n-db and libm17n-0 (Refer this thread), the m17n doesn't immediately appear on SCIM IM Engines list.

As a first step, make sure you've installed the following packages:


scim
scim-m17n
scim-gtk2-immodule


and all the other related packages.
($sudo apt-get install package-name)

As Step 2, do this:


$sudo nano /usr/share/m17n/mdb.dir


Look for:

(input-method * "*.mim")


Replace it with:

(input-method kn itrans "kn-itrans.mim")


Cheers,