ElectricSailor, there are so many things… I’ll just use a numbered list and try to be brief.
1. “Power booster and hi-gain antenna” doesn’t say anything about the signal quality. You may be stretching the link between the router and the AP a bit too far.
2. Total number of users can have an effect. The AP’s ability to support users is not infinite. I don’t know how many users you have: 1 or 2, or 30-40?
3. If the AP loses its marbles even with a wired connection to the router, then the problem is pretty simple: the router or the AP is defective.
4. Many people have trouble with configuration because the security settings get in the way of seeing problems with the wireless signal reliability. I always recommend that you establish a good link with no security first. When you’ve proved it’s reliable, then add security. So to start your troubleshooting, Broadcast SSID = Yes, no encryption, open authentication. Turn off or disable any servers/workstations with sensitive data, of course. If you still have problems, it’s a wireless issue, not a security issue.
5. Security settings do cause intermittent connection problems, despite what some people may think. Two reasons: (1) bad implementation by the vendor, and (2) marginal signal strength leading to high bit error rate (BER) causing the encrypted data to fail (because the encrypted bit stream is longer than the unencrypted bit stream, and thus more prone to corruption).
6. If the signal strength is good, but you still have intermittent operation, don’t overlook the possibility of interference. There are several sources for spectrum analyzers that look at all of the energy in the 2.4 GHz band, and not just the 802.11 signals. This is important because the interference can come from a 2.4 GHz cordless phone or a microwave oven (when it’s in use). There are some good, inexpensive spectrum analyzers that don’t have all the bells and whistles.