If Rob is referring to himself and Kristen at all I think the "problems" he means is that in their case, their respective work obligations keep them apart a lot and any couple in love wants to be together more often than not. All he means is that there is no couple is trouble-free and his "down" mood I think is because he misses Kristen. She looks beautiful in the pictures with Garrett they have taken while promoting "On the Road" but she doesn't look as happy as when she's with Rob and they miss each other. One very imporant thing Rob said here is and that is "when you are in love" so I think he has just discreetly confirmed that he and Kristen are.
If Rob is referring to himself and Kristen at all I think the "problems" he means is that in their case, their respective work obligations keep them apart a lot and any couple in love wants to be together more often than not. All he means is that there is no couple is trouble-free and his "down" mood I think is because he misses Kristen. She looks beautiful in the pictures with Garrett they have taken while promoting "On the Road" but she doesn't look as happy as when she's with Rob and they miss each other. One very imporant thing Rob said here is and that is "when you are in love" so I think he has just discreetly confirmed that he and Kristen are.