As far as I know, you're automatically subscribed to threads you post in, but you have to manually subscribe to a thread you're simply watching (haven't posted in yet). If you'd like to check your subscription settings, go to your User CP, click the Edit Options link under the Settings & Options section on the left. Find the Default Thread Subscription Mode when the new page comes up. Mine shows Instant Email Notification and I'm automatically subscribed to any thread I reply to, but I believe any option other than "Do Not Subscribe" would get the same result as far as subscribing goes (just a different frequency of emails about updates to the thread).

I get the same error after clicking the "Read All posts by ___" link in a user profile. However, when I clicked misbehave's username in her previous post in this thread, then clicked the "Find more posts by misbehave" link, it correctly took me to a page showing a list of all her posts.

Misbehave, this is just a workaround, but if clicking your own username in a post and choosing "Find more posts by misbehave" doesn't work... Try searching the site for your username. When the results come up, you can click the Curltalk tab to limit results to just posts on Curltalk. It should show all posts by you, along with any posts where someone has quoted you.
CG since 11/2011
2c /3a F /Mii, low porosity

Autumn Products /Routine:
Clarifying: Herbal Essences Tealightfully Clean, Suave Professional Deep Clean Peppermint
Low Poo: Renpure Luxurious Argan Oil
Co-washes: VO5 Kiwi Lime Squeeze or Strawberries & Cream
Tresemme Expert Selection Perfectly (un)Done, Cure Care, VO5 KLS
LI (if needed):
Tresemme Perfectly (un)Done, VO5 KLS, Cure Care
Stylers: FSG, L'Oreal Clean gel, Tresemme Flawless Curls Bouncy Curls, LALSG, HETT, AIF
PT: IAGirl's as needed