Check and keep a you eyes on the option bar text tool options. Make sure you have a contrasting color set. If you back up in the text the color you set will revert to its previous setting. White on whites doesn't show. Text layer blending opacity and fill may have been set. When a tool is not working check all settings. If all settings look good try resetting the tool.
Some actions you do in Photoshop need to be committed before they take effect before they are committed you working on setting up the action. Some things are not committed till you start perform the next thing. For example if you use the move tool you can repeatitly move a layer content around over and over. If you recording this in an action you will not see move steps being recorded. When you select an other tool or layer palette etc you will see a singe move step recorded into your action. It does seem at times that Photoshop is one step behind.
Thanks for your reply
This is very likely a computer issue. I have just determined that if I do something else, for instance, right click on an icon in the system toolbar and run it (e.g. anti-virus, greenshot), it also 'updates'.
This is not typical, and happened suddenly and is therefore unlikely to be a commitment issue.
If you have Reset your Text Tool Options, checked the color and the font's point size relative to your Image's resolution, then my next step with any display issue would be to go to your video card's mfgr's. Web site, download and install the latest video driver. Even simple OS updates can render the video driver obsolete.
AMD Catalyst 12.10, all up to date.