It's not always possible to find some files in a search (simply due to the size of the network & which ultrapeers you're connected to).

Do you see the firewall icon (brick wall in front of the blue globe)?

In LW go tools > options > bug reports > view example. Scroll down to 'recieved incoming this session'...is it true or false? If it's false then you can't recieve incoming connections from other computers & chances are that other users can't download from you. In that case, or if you see the firewall icon, please give us your details & we might be able to help a bit more.
System details - help us to help you -> Provide these details when you post!!!