[plt-scheme] Division error in DrScheme v.4.1

Hello to all! I'm just a beginner in Scheme (studying HtDP now) and now 
i have a problem with DrScheme.
When i'm calculating an expression wich returns integer values, like (/ 
45 5) or (/ 32 8), all goes just fine. But when i'm operating with 
fractions, like (/ 4 23) or (* .04 6), DrScheme returns me an error 
instead and crushes, error is

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get-extent in snip%, extracting return value via box, extracting boxed 
argument: expected argument of type <non-negative number>; given -1.0

 === context ===
C:\Program Files\PLT\collects\framework\private\text.ss:1667:4: 
do-insertion method in ...work/private/text.ss:1351:2
C:\Program Files\PLT\collects\framework\private\text.ss:1661:9
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How can i solve this?