Does placing digital circuitry between the regulators and analog circuitry cause grounding problems?
Lets look at this from the signal input direction. The correct order is A-D-R. If you are using a ADC, it would be the final analog device after all of your op-amps, etc. After the ADC all input signals are/should be digital.
The proper board layout that I use is that analog ground is isolated from digital ground. They can meet at the ADC IC or at the power source. If no ADC you still merge analog and digital grounds at the power source.
If they share the same voltage feeds (+/-5 volt would be typical), be sure to install 100uH radial lead inductors and 4.7uF 25 volt ceramic capacitors at the point where the power is used-not at the power source.
The power source has the power connector(s), and the big 470uF to 1,000uF capacitors on each voltage line to ground. This is where ground radiates out in a star pattern to the analog and digital sections. Digital and analog outputs should be close to the power source, as they have loads that often draw much more current than the inputs.
As for RF IC's, if used, layout the board as the manufacture specifies.
Two simple Golden rules to follow: Never have a digital device use an analog ground trace for a return path. All input and output grounds start at the power connectors.