Six Apart has hit more than its share of speed bumps in its short time in business, including a pricing strategy that irked users and its controversial acquisition of LiveJournal. But now the San Francisco blogging company may be facing its toughest test yet – reliability problems that are causing users to question their devotion to its flagship TypePad blogging service. Six Apart founders Mena and Ben Trott addressed the problems last month and again last week. And Six Apart employees have been trying to answer concerns in the comments sections of users’ blogs. But it seems the fixes haven’t satisfied all users. The Blog Herald posted a round-up yesterday of recent gripes from disaffected customers – admitedly a minute sampling of TypePads’s large user base.

The problems could hardly come at a worse time for Six Apart, as other hosted blogging services such as emerge to challenge TypePad.

Blogger used to be the poor-performance whipping boy in the blogging world, and they weathered the storm. Six Apart will presumably do the same. But there’s got to be a lot of furrowed brows in SA’s South of Market offices these days.