Can't say I have too much experience with those kind of problems, nor with Firefox or Apache for that matter. If it checks out now, I guess it's fine, though you may want to keep an eye on it.
Some programs give you an overall "health" and "performance" SMART read-out for a drive. PC Wizard, for example. If you see those decreasing, or they're already low, you may want to start working towards replacing the drive. 2 years isn't that old, but you never know.
