I searched around the internet first for a solution to this, but haven't found one yet, so I figured I'd see if you guys over here might know a fix.
When I click on the canvas with the text tool or drag to make a text box the flashing cursor won't show up, neither will whatever I'm trying to type, though it will appear in the name of the layer. The opacity is at 100% and the font isn't the same color as the background. Apparently this problem has been around since CS1, but the only useful suggestion I found via google was to restore Photoshop to the default presets, which didn't help.
EDIT: Turns out the resolution had somehow been set to 1, so I set it to 72 and it's working fine now.