Since I'd deleted the blc plugin files to get back my admin screens, there were left-over blc database tables, so I deleted all of them and started over.
Good news: now, no white screens.
I tried a "network activate" and in my "next" site, I received the following error:
"Database error : Table 'TABLE-NAME.wp_12_blc_links' doesn't exist"
So, I deactivated, and reactivated one site at a time. First site worked great. Subsequent sites timed out; perhaps the script was busy with the initial (major) link scan, because about 1 minute later, I refreshed the page and all of the links were accounted for (more than 500).
Overall, everything slowed down for about 10 minutes, probably during initial checking, and timed out. Then, as I activated each site, working great!
So, initial questions:
- Is there any way to throttle initial checking so it doesn't slow down the whole instance, causing timeouts?
- Would it then be possible to network activate?
That said, now that the initial check is done, all is working great (with site-by-site activation)!