Safari is glitchy since I recently yes to regular software update

Usually, when my Mac tells me that updates are available, I tell it to "remind me later," but I finally went ahead and said yes. Things have been screwy ever since, particularly with Safari and Skype.

Sometimes, when I click on the Safari icon in the dock, it doesn't bring up the Safari window. Instead I have to do "new window." Sometimes Safari won't allow me to copy and paste a URL. And it hangs or quits frequently for no apparent reason. One night it was doing that every five minutes. Aargh.

I won't go into the Skype issues since they may be unrelated and/or have something to do with my Internet connection. Except they did start at the same time as the Safari issues. Right after I said yes to the update.

I have a 2008 MacBook Pro running OS10.5.8. I have a copy of Snow Leopard, still in the shrink wrap, but haven't wanted to install it because, until just recently, everything was running perfectly and friends have reported glitches after switching to Snow Leopard.

Any thoughts?