Database table crash + send newsletters problem

Last night a desperate customer contacted me about a cart that was down. It was showing an error message about the whosonline table crashing so I did a table repair. This morning I cleaned up the old hack php files in the images directory (about 4 of them) and upgraded the cart from 1.3.8. (The patch had been applied to the cart by hand and there was no htaccess file in the images directory.)

I've checked admin files to make sure there's nothing loose in there that shouldn't be. This customer was also having trouble yesterday sending newsletters. When I tested sending the one to admin the result showed the checkmark and then a bunch of goobletygook. Looking at the source, the page crashed at that point. I checked but there is no error log so no php crash. He says that's always been the case (!)

See the result here:

So has anyone seen this happen before?

That junk you're seeing is a binary representation of the contents of the subsequent checkmark icons which should appear for each recipient being sent to. And that junk only shows when there's a problem with gzip compression on the site. Go to Admin->Configuration->GZip Compression, and turn it off.

Perfect - that worked!

Any explanation for the table crashing? Never seen that before.

Tables may "crash" if the server encounters some sort of hiccup while a record is being added/edited/deleted in the table.
High traffic tables that get a lot of use, such as whos-online, are more prone to that than others such as the "products" table which is generally read-only unless the administrator is updating a record on occasion.

Yeah, we had a second crash on that dedicated server in another cart so it's obviously related to something that happened specifically. He's in the process of moving the sites to another server. Thanks for the explanation; that's good to know.