Everything is lagging/delay - Please help! :/

Are you experiencing these delays when writing, regardless of which application you're typing on? On Finder too?

Just wondering if it may be an issue with an application or if this typing lag is happening everywhere. Also, is your keyboard wireless or wired?

Off the top of my head, provided your memory upgrade isn't the cause, I'd probably do some testing to make sure it isn't application or system related, as well as plug in a wired keyboard (if yours is wireless) just to see if the problem is present under other circumstances too.

I'm only speaking from my own experience in the past where I've had the issue on a couple of applications (and after some updates, it went away). And my sister experienced something similar once, which turned out to be a bluetooth problem of some sort.

I'm sure someone else more knowledgeable will chime in soon though, who can tell you more and whether your memory upgrade could be the culprit or not.

 

To OP :

First, test in another account, and let us know how it works there.

 

It could be a number of things, from an add-on, flash, a script hanging, a website you're viewing, etc.

First thing I'd do is update your Firefox to the latest version (including all the add-ons) if that hasn't been done yet. It could be a bug in any of those. Oh and update your Flash too. Also take a look at the Activity Monitor when the problem acts up to see there are any unusual usage/activity.

If everything is up to date and the problem persists, you can try restarting Firefox in safe mode (Help --> Restart with Add-ons Disabled...). If the problem goes away after this, chances are it's one of your add-ons causing the problem. In that case, you'd have to go in and test your add-ons one by one (unless you've recently installed something new, then chances are it's that one). Sometimes, it's not necessarily one add-on or another but a conflict between two, etc.