Did you recently update it? If so that is likely the reason, that happens if it was a major update at times

Sometimes on opening, a few bits get missed and fouls opening the page. The error message may not fit the situation. Try again. It may make it the second time. Do try again before resorting to messing with your settings.

Another problem source is the computer having difficulty acessing its RAM memeory. How long has it been since yoru memeory cards have been installed (on the mother board) and never disturbed? If it has been 2 years, that can cause trouble. These chips use low voltage and over time corrosion can cause less than good connections at the card connector. Sometimes, exercising this connector will wipe away the corrosion film and re-establish good connections. This is done by moving the memmeory card up and down a little in its connector. You do not have to completly remove the card. Open the lock-down levers at each end of the card. This raises the card a small amount. Push the card back in. Do this 2 to 3 times, and then push the card home and lock the levers.

If this was the problem, you'll see improvement in your system operation. However, failing access to the memory bank should cause other problems as well.

In the "control panel" open "System". Click the general tab (system panel) and see how much RAM memory is showing. It should match the total installed RAM memory. If you see less than the installed amount, then there is a memory access problem. Usually, if there is a problem on a memory strip, the entire card is ignored. For example, I have 2 GB of RAM using 2 cards. When a problem developed on one card, that entire card was ignored and the displayed memory fell to 1 GB.

[Another reason for not completly removing a memory card is that these are very easily ruined by static discharges. A static discharge below the limit of your sense of feel to a free standing card is enough to blow memory locations.]