I've no idea what happened, just one day recently, I went to install a package using dselect and all seemed well until I tried to use it (probably a dev pkg to compile something) and discovered it had not been installed. Some packages do install, but others, the majority don't. Sometimes they appear to be installing, other times it just completely ignores the packages I want installed.

The problem may possibly be from when I re-installed debian sarge to try out our new fancy broadband connection which only worked for two days - long enough for a basic install - before loosing all signal strength. So on HeyHoHell dialup we stayed - thus no internet for my debian box.

The only way I can install packages which cause problems is using
But a)it's a pain when the package has dependancies and the dependancies have dependancies... b)its crap to install an older package to satisfy dependancies because I downloaded a newer version in that two day window.

What may can I do to fix it?

If you're installing from CD, you should be able to add the CD to your sources using apt-cdrom add and then just do aptitude install somepackage, it will then install the dependencies from the CD as well.

The other thing you might consider, depending on how you get charged for dialup is to setup a cronjob to dialup and download only a package and it's dependencies overnight. When I was on dialup, I actually installed X, KDE, etc all over dialup. It took about 5 days at 6 hours per night to download everything (I had a second cronjob to kill the dialup at 5am). But then you can just aptitude install somepackage and it will install it from the downloaded files.

Once my system was setup, it only took like thirty minutes a week (also on a night cronjob) to download all the security updates for that week.