It's working OK for me with XP Home SP 2 and the Opera browser (although some operations seem a little slower). I installed my copy over V 3 using the previous settings, which were the default ones. Have you downloaded the V 4 user Guide in pd format? There may be something in that which would help.
You could also have a look at the NOD section over at Wilders Security Forum;
http://www.wilderssecurity.com/forumdisplay.php?f=88 As might be expected with a major update like this, lots of people seem to be having problems, and there might be a similar problem to yours mentioned.
There also seem to be particular problems for ESS users or people trying to install NOD32 or ESS V 4 on networks that include servers etc.
EDIT: Here's the link for the User Guide;
http://www.eset.co.uk/Download/Manuals