Alter index reorganize failed on an index

Dear Colleague,

I have a wierd issue with index reorganization in SQL Server 10.50.4290 Standard Edition. I've learnt from Microsoft site that the reorganization of an index always performed online, however it's just failing randomly. Later on I've seen that the alter index operation cancelled due to deadlocking. How can it be?

Snippet from Extended events:

 <victim-list>
  <victimProcess id="process53ecbc8"/>
 </victim-list>

{...}

 <inputbuf>
ALTER INDEX [IX_{...}] ON [dbo].[{...}] REORGANIZE WITH ( LOB_COMPACTION = ON )
   </inputbuf>

The "concurrent" query was a SELECT with isolationlevel="read committed (2)"

Why the index reorganize causing deadlocks? How can I avoid the deadlocking during reorganization without upgrading to EE?

Could anyone help me please?

Many thanks in advance!