strange ArrayIndexOutOfBoundsException

[Andrew Gaydenko]

HI!

On project (in fact - five related projects) compiling sbt console shows me strange warnings against nine absolutely ordinary Scala files:

[warn] /some/path/to/Some.scala:1: Unused import
[warn] package some.package
[warn] ^
... and so on

The warnings don't influence this or that way on the workflow, so I ignore them.
Being the second day digging into Emacs I'm digging into Ensime also, of course :)
Exactly against the same nine files I get on C-c C-c a:

Latest Compilation Results (q to quit, g to refresh, TAB to jump to next error)                                         

/some/path/to/Some.scala
ERROR: Presentation compiler crashed while type checking this file: java.lang.ArrayIndexOutOfBoundsException : line 1
... and so on

Any idea to cure?