I've done an awful lot of scanning over the last few years and offer a professional scanning service. Ektar is one of the more difficult films to scan for one particular reason but there are also other scanning issues that people could change to get better results.
1) Try *not* profiling your scanner and switching off all colour management when scanning negatives. A good profile is great for positives but the complex icc profile shapes can really screw around with the results when you are trying to invert. Most scanners are linear devices and a linear scan is the best starting point to do your own custom inversion (which I highly recommend).
2) Most films are linear in the center of their dynamic range. The shadows for most negative films have different toe shapes in each colour channel (or at least the same shape but they kick in at different exposures). Combine this with the fact that a lot of software trys to create a neutral black and white point quickly leads to colour crossovers.
3) Don't try and get a perfect colour balance or contrast immediately after inversion. You're looking for a fairly flat neutral colour
The second point is critical and one of the reasons Ektar causes problems. Ektar only has a couple of stops of linear response in the shadows and then immediately starts going blue or blue-violet.
I've worked on a technique in photoshops that can help with this and it's based on using 'auto' curves but changing the options.
When you have a curves layer you can alt click on the 'auto' to get the options screen up (possibly a different key combination for windows). The options pallete has the following controls (make sure you are in 'enhance per channel contrast')
for the shadows and highlights you get a target colour and a clip percentage. The key here is to change the clip percentage to a larger figure. This means that the neutral point is set up to 9.99% in from the extreme light or dark level. Typically this avoids setting a neutral point in the toe of the film or on specular highlights.
Obviously we end up with clipped highlights and shadows now. Now go into the target colour and change the brightness. If you're working on shadows, change the target colour from black to a level of grey where you can't see any clipping. Do the same for the highlights. If you can't find the exact point where clipping stops, just make the bright point a light grey and the dark point a dark grey. You can then use the auto curves in a second layer using 'enhance monochromatic contrast' with clipping levels of '0%' or '0.01%'.
The result is probably a low contrast image, now stick a nice curve on it to add contrast and bring the brightness of the mid-tones up.
Finally - use the colour balance tool to make some tweaks. A good tip when using this is to slide each slider full left for a few seconds then full right for a few seconds (and repeat a couple of times maybe). This 'clears' you visual memory of what the picture was looking like so that you can approach it with a neutral outlook.
In reality this process only takes about 30 seconds. The only final step I sometimes make is to fix the colour shift in the deep shadows. You can do this with by creating a template curve in photoshop with 8 points on each colour channel. Save this as a default which you can use as a preset on any picture. I then use the bottom point on these curves to fix any 'toe' colour issues. For instance Portra 400 has a serious magenta shift in shadows below about -3 to -4 stops. A boost in the green channel of the next to bottom point sorts this out. For Ektar you need to pull the blue channel down a bit (and potentially push the next to bottom point on the green channel up slightly).
If you have a bunch of shots in similar conditions, you can pull the whole strip in in one go, make multiple sections just picking out the image area on each frame and use this as a mask for the whole strip.
If you're interested, here's a strip of Portra 400 with each frame a whole one stop bracket. -3 on the right , +7 on the left. You can see that the shadows tend to blue-violet and the highlights tend to a yellow (with a hint of green). This is the type of colour crossover that can be difficult to deal with when looking for neutral shadows and highlights.
http://static.timparkin.co.uk/static/tmp/portra-all-compensate.jpg
