No visit possible due to Server Problems?

I do have one friend I cannot visit in the last weeks (meaning, I could 3 months ago once in a while but not anymore), as I always get a "Server Problem" Message. She is quite active otherwise (gifts'n all..) so that's what she get's from me instead, but I would like to know If that is an known problem?
Perhaps it is connected to the known Internet issue?
Could be others have the problem with me... oh, if it makes any difference - she's Russian - or so ist seems.

I have some friends like that. I have not found a solution.

It's pretty rare - only about 10 or so out of the total 600+ friends I've had.

Same problem here with one of my friends (and she is still actively playing). I can send her gifts and request gifts, but I can't visit her whatsoever anymore. Kind of sad