This has been a long time problem with TOAD (all versions including 13.2). If I am querying data containing CLOBs and I view a few - especially largish ones, at some point, editors will randomly AV or there will be some kind of memory trashing.
We did have some problems with AVs after viewing CLOBs in older versions of Toad, but I thought they were all fixed by the time Toad 13.2 came along.
If you have a Toad.el file, please send that (or, even better, next time you get the error, if the error dialog has a "click here" link, then click it, and on the next dialog, check the 'Copy to clipboard' checkbox, then click OK and post the error log here)
Let me know which database and client version you are using