Problem with phone storage space

I have a problem with my phone storage space. I use Modaco R9 2.2 custom rom on my Htc-Desire phone. I installed a few softwares on sd card not on phone memory but i got this message :
"phone storage space is getting low"
Then I tried to unistall all the new apps but the phone storage space is still full and i can't install any application on my phone. This is so bad. :(
please help me.