I wouldn't suspect the laptop is faulty, assuming that you are able to perform other network activities with it (internet, email, etc.) Especially since you report that it can "see the folders"
Your suspicion that the "different AntiVirus" product may be at the root of the problem is a good one. So a relatively easy proof of concept would be to uninstall the antivirus software. There are some helpful links to top tier vendor's proprietary uninstallers here Link Removed if your's is not included use google to find the uninstaller from your specific vendor.
If after uninstalling and rebooting the problem is resolved then you've found the culprit. If not you can always re-install it later.
Perhaps take a look at this article and...