I had already posted about this (http://drupal.org/node/65049), but I'm posting about it again because I found that the problem is not specific to Textile. This is happening with any module I'm trying to install...
They're simply not showing up after I upload them. I know I am putting the modules in the right place; earlier I had installed poormanscron and pathauto without problems. Then I uploaded Textile the same way (and INSTALL.txt verified that this is the correct way), and it didn't show up. That is, the module list skipped right from "taxonomy" to "throttle". I did a little temporary hacking of system.module to try to uncover the problem, and it turned out that system_listing was not finding the module when called by system_modules. I gave up, reverted system.module to its standard version, and went to bed. Then when I got up and logged back on, poof, there was Textile! That's strange, I hadn't done anything since I had last checked it, but there it was. So today I tried to install the interwiki module, and... that's not showing up either. As a test, I uploaded pathauto again (I had deleted it since I decided I wasn't going to use it), and that's also not showing up even though it had installed fine before.
What's going on here? Does it just take a godawful long time for the system to find them for some reason? And if so, why's it taking forever when it found poormanscron and pathauto (the first time I installed it) instantly?