I have a hotspot installed, many users connected, some of them has a problem with login. Their browser (does not matter if Firefox, IE or Chrome) are failing to connect to hotspot login page. I am using hotspot many years, it happened 5-6 times, everything this year and each case is with a user with Win7 (but others with Win7 are OK) and each time with LAN (cable) connection. The same user if using Wifi connection to the same hotspot network receives login page correctly ... Any ideas? Thanks.

Is the splash (login page) appearing?
If it is what error are they getting when they attempt to log in? It will be in teeny tiny red font at the bottom of the login page.

If not, are we sure they are getting a valid IP from the RB? Win 7 should at some point ask if it is a home/work/public network and then validate internet connectivity. This could be why it is happening only in 7.
Also, try having them disable ipv6 in TCPIP settings. I have seen this cause a similar issue.
Also, there are 3 or 4 flavors of win7. See if the folks having trouble are using the same version.

are those users login/logout a lot? cause one time i saw such behavior when hotspot locked me out and i have to restart the router. happened only once tho. ironically, i was using win7. also its worthy to note that win7 kernel, handles network packets really weirdly. if it fails to reach a host, it tries to reroute the packets, ignoring all the routing tables.
does only rebooting the router solve the problem?