I have seen this a few times on my slingcatcher.
In every case, I have simply restarted the catcher (by quickly pressing the reset button on the back of the catcher - not a long press which causes a factory default reset), then it works.
I am not sure the cause of the issue. I do not think it is at the slingbox end because both my boxes work with the pc, but the catcher complains about the network. It seems to be that the catcher does not correctly get something from the router. But it is connected to my account and shows the available slingboxes. Its a bit strange.
I have seen this happen at my home (in Shanghai) and in a hotel where I am now in North West China.
I am not using fixed ip address for the catcher.
But once connected, the catcher does a superb job. Pity sling stopped selling them.