I have been using the same set-up and layouts for over a year and this just started a month or so ago.
The million-dollar question then is: "what changed?"
OS updates, hardware changes, software update, schema changes on the SQL side,...
If you constantly find the same need to view SQL data, see if you can create a view that is already sorted so that FM does not have to do the sorting.
ESS can be particularly finicky with large sets of data. Are you in list or table view? If so, try to limit the found set to 25 records. If you are in Form view, does it have a portal to the ESS table that finds the whole found set or something really long? FileMaker rarely stops working, but pulling over all that data and recalling maybe unstored calcs can take it a long time.
There always can be driver or OS issues. If you haven't checked, make sure your drive is current with the version of FileMaker you are using and the ESS database is compatible too.
FileMaker has to do a lot of shadow table tricks to make ESS work whereas a regular ODBC import or Execute SQL script step tends to have less compatibility problems to fall back on. Then again, I'm doing a lot more of these type of transaction calls to other solutions via RESTful APIs which are very fast and reliable.
But there sure is a lot of elegance with ESS when it works right.