Time machine won't finish backup

Question

I have been trying for the last three days to back up my computer using my Time Machine and I'm not having much luck.  The backup was stuck for 4 hours at 4GB out of 42GB so I stopped the backup and did some software updating and clearing off of the hard drive and started again.  The same thing happened.  This latest attempt (still running) started at 9pm last night and it's now 8am and it's only at 8GB and is not moving (so it might have been stuck at 8 for awhile).  I want to backup my computer before I install Mountain Lion (I'm using Lion), but am having no luck in getting the backup to finish.  Any ideas?
I do have 611GB free on my hard drive and haven't had this issue before to this extent (I've had very very slow backups - but never this long).
Thanks
Nicole

Answer 1

You should remove "Avast" whether it's causing the problem or not. It will never do anything but slow down and destabilize your computer. This wouldn't be the first time in my experience that a commercial "anti-virus" product has caused a problem like yours.
If you still have slow TM backups after removing Avast, post again.
This comment applies to malicious software ("malware") that is installed unwittingly by the victim of an attack. It does not apply to software, such as keystroke loggers, that may be installed deliberately by an attacker who has hands-on access to the victim's computer. That threat is in a different category, and there's no easy way to defend against it. If you have reason to suspect that you're the target of such an attack, you need expert help. OS X versions 10.6.7 and later have built-in detection of known Mac malware in downloaded files. The recognition database is automatically updated once a day; however, you shouldn't rely on it, because the attackers are always at least a day ahead of the defenders. In most cases, there’s no benefit from any other automated protection against malware. The most effective defense against malware attacks is your own intelligence. All known malware on the Internet that affects a fully-updated installation of OS X 10.6 or later takes the form of trojans, which can only work if the victim is duped into running them. If you're smarter than the malware attacker thinks you are, you won't be duped. That means, primarily, that you never install software from an untrustworthy source. How do you know a source is untrustworthy? 
Any website that prompts you to install a “codec,” “plug-in,” or “certificate” that comes from that same site, or an unknown site, merely in order to use the site, is untrustworthy.
A web operator who tells you that you have a “virus,” or that anything else is wrong with your computer, or that you have won a prize in a contest you never entered, is trying to commit a crime with you as the victim. [Some reputable websites did legitimately warn users who were infected with the "DNSChanger" malware. That exception to this rule no longer applies.]
“Cracked” copies of commercial software downloaded from a bittorrent are likely to be infected.
Software with a corporate brand, such as Adobe Flash Player, must be downloaded directly from the developer’s website. No intermediary is acceptable.
 You should disable Java (not JavaScript) in your web browsers. Few websites have Java content nowadays, so you won’t be missing much. This setting is mandatory in OS X 10.5.8 or earlier, because Java in those versions has bugs that make it unsafe to use on the Internet. Those bugs will never be fixed, because those older operating systems are no longer being maintained by Apple. Upgrade to a newer version of OS X as soon as you can. Follow these guidelines, and you’ll be as safe from malware as you can reasonably be. Never install any commercial "anti-virus" products for the Mac, as they all do more harm than good. If you need to be able to detect Windows malware in your files, use the free software ClamXav — nothing else.