UCMAPI.EXE Locks Outlook OST File

I am investigating an issue in our environment where the Microsoft Lync client is locking the Outlook .ost file and preventing Outlook from updating it.  This results in the user not receiving any e-mail.  The offending process is UCMAPI.EXE, which upon examination using ProcExp shows a number of "mutant" handles manipulating the .ost file.  Upon terminating those handles, the .ost is freed up, the sharing violation ceases and the user is able to receive mail again.

Please advise.

Thank you,

Doug