UK gamers believer they're bumping into that country's mandatory ISP-level smut filters, courtesy of a filename that accidentally red-flags the purience-punting grumble-blockers.
Courtesy of this Reddit thread, it seems that users trying to download upgrades to the game League of Legends are stalling when they reach files called VarusExpirationTimer.luaobj and XerathMageChainsExtended.luaobj. Both of the files include the sequence s-e-x in the filename: not so much a “false positive” as a “true positive by accident” combined with an extreme case of don't-even-mention-the-word Victorian morality.
The Guardian notes that the filters are currently only used by a minority of people: those that have ordered a new service since the law came into effect, and who said “yes” to filtering when they signed up.
If it is the porn filter catching the files, it seems to The Register that Riot Games could shoulder some small amount of the blame, because the issue has arisen before. Here is one forum thread from 2013 in which the same file was getting stuck, and users didn't know why; and another from 2012.
Alternatively, the problem could have nothing to do with the UK filter, but rather reside back at Riot Games: for some reason, in heavy update traffic, its servers stall on those files in particular. The Register has sought comment from Riot Games on the issue.
The Register also wonders what would happen if Microsoft or Oracle were to accidentally slip a sequence of letters into a filename that upset a smut-filter. If that were to happen for a zero-day emergency patch, it wouldn't be a small number of gamers that hit the ceiling... ®