It might just be your sources you're downlding from at that time. Or it might be your isp. Tiscali have been known to filter p2p sharing speeds in some locations (yes their company have outlets across Europe.) See ISP's known to BLOCK or Filter p2p or specifically Limewire

To help your issue though, see the following link & follow all the off-shoot links to find hints & extra skills to help: To continue files downlding (click on link)