Neither PASV nor PORT mode establish a data connection


For the last fiew weeks i'v been getting these errors over and over again on any ftp client I use,i mainly use SmartFTP but i'v tried WS_FTP,CuteFTP,3D FTP,Crystal FTP,FireFTP and FileZilla but they all get the same problem.I thought it might of been my host so i changed two or three times just to see if I could get it to connect,but nothing.I keep getting the 425 error and if I untick Passive mode I get the 500 error.

Someone suggest to connect to as a test if it might be my ISP and It connects to it using port mode but when I try passive mode it gives me the 425 error.I seem to be able to connect sometimes to a few host in Port mode but when I try to upload something it just time's out & when I retry after it doesn't connect.

I dont have a router,and I have tried turning off my ZoneAlarm free firewall ( I tried uninstalling it aswell) and I cannot select which ports to open in ZoneAlarm but it always worked fine with the FTP and Avast Anti Virus,I even used a application called EndItAll to kill any programs running in the proccess manager that are non related to the system.I Run on windows XP with SP2 and dont use the windows firewall,is their any software known to be blocking the connection of ftp clients? I have a couple of hundreds of applications install but this never happend it always connected fine.A few days ago I left it connected in port mode to and when I tried to change and use passive mode and connect it worked,then i closed the ftp and opened it again and tried to connect directly in passive mode but got 425 again.I have posted in some support forums but nobody seems to know the answer,I would rarely ask for help but this problem is really frustrating me cause i'v tried everything and I recently purchased a premium hosting plan and can't access it cause of this problem.Any help is very appreciated.

thanks in advance

kind regards