downloading problems on client computers

Hello everyone
I am using ccproxy from some time and it was working alright but recently I upgraded my internet speed package and since then there are some issues e.g. internet browsing on client computers is fine but softwares and files like pdf, ppt are not downloading. sometime download prompt window appears sometime not and even if download window appears, download does not start instead same file/application request of downloading shows on server PC (where ccproxy is runing) if I OK from there it downloads otherwise not. I haven't changed any settings on ccproxy and I am sure about IP settings of client PC's is fine.