Here's another bug which as quite a bit more info: https://bugs.maemo.org/show_bug.cgi?id=417

One of the comments recommends your same solution of using the manual name. I'll try this tomorrow, but I highly doubt it will work since the only way to get to this screen is to change the network type to WPA when it should be WEP. If I do change it to WPA, then I'm not able to see the custom network when scanning for networks.