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.FileSystemEnumerableIterator`1..ctor(String path, String originalUserPath, String searchPattern, SearchOption searchOption, SearchResultHandler`1 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?