Hawaii gives us a glimpse of the future of what solar will look like in the US. They are the hottest solar market in the US due to having the highest electricity rates combined with excellent conditions for solar. The primary utility in Hawaii (HECO), has started denying many permits to homeowners due to grid saturation on many circuits.
Infrastructure investments must now be done by HECO to allow for increased solar adoption - something that may not be in the best interest for the utility.
I'm not positive, but I might imagine that it's that the solar power generated by that particular grid either equals or exceeds the amount used by it. If there's multiple grids it could be that the residential area is nearly self sustaining during the day, and they don't have the capability to move that generation successfully to the other places that need it because the grid interchanges weren't built with that in mind.
The other option is to grid-tie, but agree not to sell any power back to them (which can be configured in the inverter). You would then use utility power when you don't have enough solar output to meet your needs.
Disclaimer: I have read WAY too much Home Power magazine over the last decade. I could design said system in about 20 minutes, part numbers and all. [http://www.homepower.com/]
Infrastructure investments must now be done by HECO to allow for increased solar adoption - something that may not be in the best interest for the utility.