Hello, first post on this nice forum

Excuse me if I make a mistake!
First, I have 750k BB (I got my upgrade 1st August) with a Surfboard 4100 modem connected via 10/100 Nic to an AMD XP1900+ PC, 512mb RAM.
Now, I wondered if anyone could help with a problem I have? About a week ago I was able to upload file attachments to my Hotmail and Yahoo e-mails, as well as upload files to my Yahoo Briefcase. Now all of a sudden, within the last week, I cannot do this anymore? I can send e-mails, just cannot upload files to these accounts. Attachments just time out while uploading and Briefcase says files have been uploaded yet my folders are empty. Nothing has changed on my PC and I use Zone Alarm and AdSubtract for security as well as Norton Antivirus! I even re-installed WinXP Pro this morning plus all critical updates, rebooted the modem, and tried uploading to hotmail/yahoo without any firewall/ad blocker or anti virus loaded (XP firewall turned off too!), and the same problem occurs, cannot upload files to hotmail/yahoo!
If I use a friends PC, who is on BT Broadband, then I do not have a problem as I can attach files to my hotmail/yahoo e-mails and upload files to my yahoo briefcase, this is puzzling as it suggests an NTL problem?
I did contact NTL and was told yahoo/hotmail are not supported by NTL and to try my PC on my friends BT connection to see if I could upload files, I have yet to try this, but seeing as these are WEB BASED services file uploads should not be affected should they? My browser uploads requests for web pages so data is being uploaded there, so why not a file upload? It was only a 10k mouse driver I was trying to upload!
There was an outage las week in the NG16, NG17 (my area) and NG18 areas that knocked the connection off from 10pm one night to mid afternoon the next day, and maybe coincidence, after that outage my problem was discovered.
Has anyone else had problems uploading files to Yahoo or Hotmail via NTL? I'm not a novice to computers so don't be afraid of technical suggestions, I'd just like to know why this has happened! I've tried a couple of different web proxy servers (Leeds, Dublin and default of Notts) and still the same problem! I've also Rebooted the modem more times than I can remember and changed the channel ID in the modem, all with no luck!
So, suggestions please anyone?