Dad's computer wouldn't connect to our desktop machine, but it would connect to our laptop (Vista to Vista), so I knew it wasn't the router or NAT or similar that was blocking access.
Both machines run McAfee and it turned out that on the laptop the firewall had been configured to give Windows Remote Assistance (msra.exe) Full Access, while on the desktop it was set to Outbound Only.
Changing the firewall settings for the program on the desktop to Full Access fixed it!
When developing modules it can be useful to increase the level of error reporting within Drupal. To do this (in D6) edit common.inc and change the line
<?php
if ($errno & (E_ALL ^ E_NOTICE)) {
?>to
<?php
if ($errno & (E_ALL)) {
?>This will report all errors, including notices, whereas normally they are suppressed.
I am doing some work on a new Drupal module at the moment that will add my flash node functions to the content constructor kit (CCK) (see the FlashField project page for details). It had all been working well until today when I installed the Flash Player 10 update, and then the content no longer appeared in Firefox or Safari.
A bit of fault finding pinned it down to using the private file system, and then only private files associated with the FileField module (which my new FlashField module relies on).