Why don't you try installing a newer firefox? The current version 1.0.6 is much better then the standard 1.0.2 on Mandrake.
You can download a package here:
Careful with this repository thought .... it's said to have some broken packages, but firefox and thunderbird are working wonderfully for me.
If you have trouble installing the rpm package (rpm -Uvh <package name>) I'll help you.
[Edit to add]On "Edit" ---> "Preferences" there are some networking configuration. You could try to change them ...