Potental signs of a failing harddrive?

I would back the drive up to an external using Time Machine. Then start up from your system installation disk. Go to the second screen pull down men to Utilities -> Disk Utility. Select the drive on the left and reformat the drive using the write zero's option. This will map out any bad blocks that may have developed and not write to them anymore. Repairing errors and then rewriting to those same bad blocks will just keep giving you errors till something that the system has to have gets written to them, then it's reinstall the system and hope your system doesn't hit the same pot hole. After the drive is zeroed, use migration assistant to bring your data back. Then run the repair till its clear. After doing all this and you still have problems, it's time for a new drive.