Lead duplicate creation

Hi,

I have a problem on create and delete Lead.

  1. CRM show that there is duplicate lead when I’m saving new lead with just Account name - but there is no duplicate and duplicate window is empty
  2. Whenever I delete lead in log there is this:

[ERROR] Unable to get proper side for link contact
[ERROR] Unable to get proper side for link contact
[ERROR] Unable to get proper side for link contact
[ERROR] Unable to get proper side for link contact

The same error I got for the 1. and 2., and it is always 4 errors on one lead.

Anyone have some explanation?
Filip