All conversations in Lync for this calendar year are corrupt in the Converstion History folder of Outlook 2013.
They appear like
Full Name [12:50 PM]:
ÿþ<
The date/time and number of conversations listed are correct. However the conversation is not readable, and is always "ÿþ<"
Obviously something has changed since the start of the calendar year
Using Microsoft Lync 2013 (15.0.4551.1007) 32 bit
Alex