Not enough detail yet to pin down a cause.
"rs_logexec" is used as a transaction name in many of the system stored procedures.
Output from the following may help narrow down what is happening, substitute the spid of the blocking process in the commands below::
dbcc traceon(3604)
go
dbcc sqltext(<spid>)
go
dbcc stacktrace(<spid>)
go
--object id of the procedure being executed:
select id from master..sysprocesses where spid = <spid>
go
-bret