Files fail to send

Hi
I've two problems, possible connected.
Prob 1: I use a package [PTP] to do tax rtns [UK] which on completion I transmit to HMRC. I recently found that it wld not send them. I reporte the error msg to the vendor but they said it wasn't there s/w, no else had reported, it must be my AV or fiewall. So I contacted AVG [I've comm'l lecence for their internet suite] and as advised uninstalled it and switched off the f/wall. Still won't send.

In the meantime I've used my laptop, it already had PTP on it as it used to be my 'PC' before reverting to desktop. It works fine. Several updates from PTP later and still my desktop does not send. Any clues what might be stopping it?

Prob 2: Companies accounts are submitted to Companies House by d/l'd a PDF from Co Hse, editing it and resending, all within the PDF. Shortly after prob 1 arose I discovered I cannot send the PDF from my desktop but I can open the PDF on my laptop and it will go. Any clues, are these two problems connected?

BTW, my wife's PC [my old one] also sends both. My new PC was initially set up using an image file from my old one last Dec [08] and has worked in both cases.

Systems: Dlink router and modem [2 units], both desktops running Win XP Pro and laptop Win XP Pro media, auto updates, both running AVG Internet suite updated every 3 hours.

Regards

Mark