I'd suspect it's timing out.
How many computers (Win / Lin / OSX / AIX / etc) in your DB?
A linux PC can have literally a couple of thousand of software entries.
I am working on enabling paging in dataTables. Hence the front end would request 10 / 100 / 1000 rows at a time and be much more responsive. Currently it simply downloads ALL rows to the browser - which if there are 10's of thousands.....
You could look at the php.ini and extend the timeouts. Specifically check out max_execution_time and memory_limit. And naturally you can always throw more hardware at it
Another thing to check is the non-current rows in the database. You can see them on the menu -> Admin -> Database Maintenance page. You can also click the X icon and delete them.