rendering a very easy formula with greek text in it produces a pdf-document that has not  a valid utf-8 string.

I use evince for displaying pdfs under ubuntu linux. The document appears correctly on the screen but stops printing after a greek letter in a formula.

The error-report says:

Internal Error: cairo context error: input string not valid UTF-8

The same document compiled in live.contextgarden.net doesn't produce a mistake and can be printed with evince.

I can still print the document correctly using 'lpr name.pdf', so it's not a big problem for me. But I don't know if that could be a problem for someone else.

Test-Document: