All, please help me - it is very urgent

I use SMARTFTP Client (English version). It was working properly but since I changed my modem to WIRELESS - I could not connect to my website host - because of that I could not update my site. I am in great pressure to solve the issue. I tried googling but i could not get any help in any of the websites.

Somebody said that I would force PASSIVE FTP - when I did - the FTP 500 Error did not come but I still could not LIST the directory, upload the files.

Somebody said that the problem with MSDL but I do not know how to disable that.

Please help... Please help..