LT3758 radiated emmisions test failed

Hallo, I designed a flyback power supply using the LT3758 who works fine. The only problem is that the radiated emmision test from the unit failes in the frequency range 30Mhz-100Mhz (see picture M08.EMF). You can find the schematic from the supply in DU9_ps.jpg. Is there anybody who can give me a tip?

If I power the unit wth an external 5V supply then the values between 30Mhz and 100Mhz are much lower. thats why I suspect the LT3758 power supply.