Path is not of legal form? what path?

Guys,

warning message:

08:25:52 System.ArgumentException: The path is not of a legal form. at System.IO.Path.NewNormalizePath(String path, Int32 maxPathLength, Boolean expandShortPaths) at System.IO.Path.NormalizePath(String path, Boolean fullCheck, Int32 maxPathLength, Boolean expandShortPaths) at System.IO.Path.GetFullPathInternal(String path) at System.IO.FileSystemEnumerableIterator1..ctor(String path, String originalUserPath, String searchPattern, SearchOption searchOption, SearchResultHandler1 resultHandler, Boolean checkHost) at System.IO.Directory.GetFiles(String path, String searchPattern, SearchOption searchOption) at StockSharp.Hydra.Tools.ImportTask.OnProcess() at StockSharp.Hydra.Core.BaseHydraTask.<Start>b__81_0()

All paths I have specified are correctly formed. What path triggers this warning?