I ran into the same issue with an E2500 and returned it but subsequently discovered the issue is with the Galaxy Tab 10.1. When you specify automatic channel assignement the router may choose a channel in the higher part of the band around 5.7GHz. This does not work with the Samsung... you must assign a chennel in the low part of the band in the 5.4GHz segment. Then it will work fine. This would seem to be a bug with the Galaxy 10.1.
I found out this is also a problem with my Note 10.1.
If I set the 5GHz band to be in the 5.4GHz channels, the Note 10.1 can see the 5GHz WiFi, but if I set it to channels above 5.7GHz or Auto, it will not see the 5GHz WiFi.
Anyone have some experience with this?