Hi, you can rescue magenta cast in LR2. Use the adjustment brush, set the type to saturation, set the level to -100%, set the colour to magenta (hue about 300 degrees I think and) and start painting away on the affected area. Feel free to experiment.
Alternatively, get IR filters, which will result in loss of red (cyan drift) at the edges. This can also be fixed in LR2 by using a red grad filter at a low level of saturation (~10%). Works a treat and can save that alone as a preset to apply to all your files. Will need tweaking for each lense but works well.