Info I got from D-Link:
"If the connection is dropping after a few seconds -- then a couple of things to check: Wi-Fi password entered not matching, mismatching encryption settings, beyond the range of coverage --probably not the case for the user, or might be a incompatibility issue.
The DGL-5500 has been tested with Broadcom based, Intel based, and Realtek based adapters - so I do not think that this is the issue.
The DGL-5500 has been tested by the Wi-Fi Alliance in their test bed for compatibility with other adapters from different vendors."