maxima fail... how I can find error?

I use maxima. My step:
[yan@home ~]$ maxima
Maxima 5.13.0 http://maxima.sourceforge.net
Using Lisp GNU Common Lisp (GCL) GCL 2.6.7 (aka GCL)
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
This is a development version of Maxima. The function bug_report()
provides bug reporting information.
(%i1) 1+2 //Maxima not solve expression and I interrupt it (press Ctrl-C), maxima notify:

Maxima encountered a Lisp error:

 Console interrupt.

Automatically continuing.
To reenable the Lisp debugger set *debugger-hook* to nil.
(%i1)               


Why maxima not solve 1+2 ?
How I can find error?


Best regards,
Yan.