Hi to the OSX experts

I have an eMac and have just migrated from 9.2 to OS 10.1.5 on the same machine. While in 9.2, I had slow downloading and achieved roughly a 5% success rate. Uploading was significantly better. About 30% of uploads were successful and at speeds I could only dream about. However, now that I have made the change, uploads have all but disappeared to about 1% successful at a snail's pace (1/2 kb/s). Downloading is about the same with speeds around 4kb/s. I have been in OSX for five days and have received seven abusive chat messages complaining about their failure to obtain any of my 1,000 plus files. I can understand their frustration.

I am not behind a router.
I have an Aztech ADSL and an unlimited 512 account.
I have been into System Preferences and turned on File Sharing and FTP Access.
LW preferences are at maximum for uploads at 20 slots min and max (although I have never seen more than eight at work at any one time).

All to no avail.

So, please advise what to do next so that I can give as well as take.

Thanks

David