Just began encountering an Network Update issue on WP 3.3.2 multisite installation with about 45 sites on it. Has multi domains active and domain mapping active. Have not ever had this issue in last two years, but recently the Update Network process has started failing after the same blog every time and will not complete.
25+ other blogs update fine and then......
Warning! Problem updating . Your server may not be able to connect to sites running on it. Error message: A valid URL was not provided.
Any advice about where I should look for the missing or invalid url that is referred to in the error message?