GRE/Taking GRE the Second time
You have been the victim of empty rumors. You can take the GRE as many times as you want. ETS will report your 3 latest scores and it is up to the school to decide which GRE score to take.
Many schools in the US will have their own algorithms and methods. The only way to find out is by asking graduate admissions of specific schools directly. They may or may not tell you of their policies.
If they do not tell you about their policy - which is what they should do - you have no way of knowing which score is taken.
In the US, people like to take the tests one - two times or more. For example, kids routinely take the SATs multiple times.
In any case, if you are able to tell us the names of the forums where you heard this shocking nonsense about second attempts, it would be very helpful to warn future aspirants of such forums.
Coming back to you in specific, if you feel the GRE score you received does not reflect your expectations based on your innate intelligence and test-taking skills (watch the careful wording there, its not your fault, its the test's! - that's how you believe in yourself and sell yourself), you are welcome to take it again and we would like to help you as much as we can.