Help! iTunes is making my iMac act like a Windows machine!

Question

Here is the basic problem:
Some songs will not play properly in iTunes, pausing often and causing the spinning beach ball of death to freeze my iMac for 5 to 10 minutes at a time, sometimes longer. I am also having problems ripping those songs to a CD.
I am trying to decide if I should uninstall iTunes or simply back everything up and do a clean install of Snow Leopard and iTunes.
I’m also wondering if simply getting more RAM would solve my woes. I have 2GB, which worked well for years. I have 4GB coming in the mail.
I have a 2008 iMac. It has about 175GB of free space on its hard drive, about 144 GB in use. With iTunes playing a file and nothing of particular note open, it has just under 1GB of free system memory, or RAM. I have both the latest version of Snow Leopard and iTunes installed. All software is up to date. Except, of course, that I'm not running Lion.
I have a 45GB in music and 54GB in podcasts in my iTunes library.
I have corrected my hard drive’s permissions repeatedly but am unaware of any other maintenance I should be doing on my hard drive.
Here are some observations that may or may not be helpful:
Songs in the same folder are behaving differently, some consistently playing without a problem, others consistently spinning the beach ball.  For example, five songs off an album will freeze up my iMac but the album’s other songs do not.
I can, however, duplicate the symptoms with otherwise dependable songs by having more applications open. Nothing major, say Safari, Finder and iTunes. What I don’t get is why some songs would play well and others not when only iTunes is open.
Having a handful of applications open now sometimes prompts the spinning beach ball of death. This never used to happen, hence the RAM coming in the mail.
When I check information on the malfunctioning music files, it shows they contain data, but I start getting the beach ball checking  the file’s “sharing & permissions” status in "Get Info."
Interestingly, I recently had to stop backing up my podcasts in Time Machine because some of them were crashing it. My music files, however, have been backing up fine in Time Machine, so far.
Also, when I try to copy my music files onto an external drive or my desk top – in anticipation of reinstalling iTunes -- my iMac cites error 36 and stops the process.
My iMac’s performace problems started to occur before I finally updated to Snow Leopard a few months ago. Indeed, I thought updating would solve them.
I had been regularly updating iTunes, however, I recall reading somewhere that upgrading to Snow Leopard while having an up-to-date iTunes installed might cause problems.
There you have it. Any advice or insights would he most welcome.

Answer 1

Well, I seem to have solved my own problem. Do I get 10 points, I wonder? It appears that my poor iMac was in desperate need of a masssive cleaning. Thanks to other posts here and elsewhere, I found out about Cocktail, a free download -- unless you chip in for the more advanced version. This is a powerful and easy to understand tool. I used it to perk my iMac up to a level I have not seen in a LONG time. The spinning beach ball of death must go play elsewhere.  Among other things, I cleared out all my caches, eliminated a ton of foreign languages and did several repairs, including tracking down and killing a corrupted permission. It also taught me how to tap into my computer's activity logs and gave me other useful insights. GOOD stuff. I did other things not related to Cocktail to free up processing power -- such as turning off file- size view option in Finder -- but Cocktail is what solved this problem. As I type this, I am happily listening to songs that earlier would not play. What a relief. I am now especially looking forward to that new RAM. We'll be blazing fast then, by gum.