Yes, the problem arises during improper handling (e.g. thawing directly in water, etc.), not from freezing (have a look into research on factors affecting loss of nutrients, vitamins, minerals, etc. - you will see that none are affected by freezing).
For starters, we must ensure that the word nutrient is not used incorrectly. For example, many people use the word nutrient to describe a vitamin for some reason. For our purposes, nutrients refer only to proteins, carbohydrates and lipids - and there is not a single legitimate (peer-reviewed) study that found significantly different levels of nutrients before and after freezing.
Now, as mentioned, some problems arise with vitamin levels during the thawing process. Many water soluble vitamins can leach into water, or degrade with prolonged exposure to oxygen, high heat or light, etc. However, as mentioned, this would be considered improper handling techniques and the losses are not significant anyway (may be due to sampling error), so the point is moot.
If handled properly (for example, thawed in a Ziploc bag in warm water and fed as soon as possible), there are no significant differences in nutrients, vitamins, minerals (inorganic), etc.
Some quick searches should provide you with the information you requested.
