Uploads > ~800k fail

Hi,

Until a few months ago had no problems uploading files to Flickr. Am a pro member with unlimited allowance and max filesize 50mb - but can't use either the web form or flickr uploadr or email.

Have a Belkin wireless 4 port router 11b +11g mixed mode 100Mb/s

Can't send file of 4.3mb via email - BT max email file size limit is 25mb.
have (supposedly) 20mb service,
max uploadspeed is about 358kb/s before upload fails.
Flickr uploadr failure seems to indicate that app is execting a "ticket" - but can find no info to tell me which ports I need to open or nat rules if any.

Webmail just barfs and hangs ( both new and classic mode)

It's not just Flickr, Picasa and other services have same problem - seem to be file size related

Have tried enabling ftp ports and web ports on router but no difference
seeing no errors on windows firewall or on router firewall

Running out of ideas - please help - wondering if it is interleaving issue but not sure how to go further to diagnose

thanks

Additional detail

BT Yahool Mail "Internal Error"
Flickr Uploadr consolejs line 144 unexpected error

Same problem even after disabling both windows defender and router firewall
Tried in Chrome, Firefox, Opera, IE 8
Tried email upload with outlook and webmail, googlemail and btyahoo mail
All can browse to attach file, then hang
have tried variety of files
getting desparate
retried above after disabling avg linkscanner

Please please please - which settings do I need ?

Thanks
Zeph

I'd try from a different computer. Perhaps some settings have become corrupted on yours.

thanks - have tried from my mac and my linux sever - no joy

pathping 100% packet loss on hop 4 - 5 ( before it gets to dns) after about 244kb or 896kb - then upload fails

tried tweaking rwin but 1.19mb is best I've achieved - not enough files are ~4.5mb

webmail upload also fails but can send from outlook but it's v v vslow ( 4kb/s - to 60kb/s)

running out of ideas - any help would be gratefully received.

Thanks - Zeph

Who is your ISP and what MTU setting are you using on your router?