IE10 throws System.AccessViolation or hangs (buffer overflow) after update

After yesterday's update of IE10, it reports :

An unhandled exception of type 'System.AccessViolationException' occurred in mscorlib.dll

Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

tested this on several machines, this only happens after the update to version 10.0.9200.16618 (10.0.6) KB2838727 . The message appears after using showModalDialog with a url that is longer than 255(?) characters and then navigating away (location.href=...) in the parent window. 

This used to work ok, I think I am overflowing a buffer (serious problem!).