[plt-scheme] Problem with debugging (time (sin 3)).

If I try to step through that program, it opens Standard Output with message

+: expects type <number> as 1st argument, given: #f; other arguments 
were: 0 -1

 === context ===
C:\Program Files\PLT\collects\mztake\debug-tool.ss:791:12
C:\Program Files\PLT\collects\mztake\debug-tool.ss:805:23
C:\Program Files\PLT\collects\mztake\debug-tool.ss:804:10: can-step-out?

I've seen same error in other programs, not using (time ...)
Standard methods for submitting bug reports do not work at the moment.

Thank you,
Majorinc Kazimir