avast! Network and Web Shield

I’m wondering if the Network and Web Shield slow down your internet. Lately, it’s been kind of sluggish, more sluggish than usual, so I don’t know if it’s just my very unreliable ISP or if it’s avast!

They don’t slow down mine, but every system is different, win XP Pro ans win7 systems both with the same firewall, avast! and resident anti-malware.