That Diablo II version 1.13 patch first mentioned back in March and said to be hitting the test real "soon" about a month ago has suffered another setback (thanks Ant via Planet Diablo). The post announcing the patch in March now sports its fourth update, explaining the latest problem:

The Diablo II 1.13 patch is on temporary hold while we investigate potential impact on the Battle.net service. As we moved closer to launching the patch concerns grew that an increase in the player stash size (a feature in the patch) could compromise the Diablo II Battle.net service. The hardware and configuration could potentially not handle the increased stash size gracefully under heavy load. Currently we’re investigating potential impact as it is one of the larger content features in the patch and we’re hoping it can remain a part of the release. If it does have to be removed it will require additional time to remove it, generate new patches, and test, which will add time before we can go live on the PTR.

We’re hoping to have our diagnostics and a final decision on how we’ll be moving forward decided by early next week and we’ll have an update for you at that time.