Two week ago, I installed Callibre 64 on a fresh new PC with Windows 8.1 Pro (64b) But now, I can't download the metadata anymore. It will time-out and give me an error on every book I look for. It worked OK on my old PC with windows 7 (32b). After that, my netwerk LAN internet connection is very slow or complete gone. I have to restart the PC to bring back my LAN internet connection.
After a new PC startup my connection is back. In safemode, Calibre and downloading metadata works well. This only happens with Calibre. I tried the 32b version: same problem. I have the latest realtek LAN drivers for , the latest motherboard firmware (Gigabyte GA-B85M-HD-3) for my on-board PCIe family Controller. After losing connection, I flushed DNS, reset winsock, disabled IP6 in LAN driver, but nothing helps. I may be a windows 8.1 problem, but for me, it only happens with running Calibre, loading internet meta data. Am I the only one with this problem ?

Any advice on how to solve this would be welcome !