Photoshop :: Text Layer Needs To Be Updated ?

I save a CS3 .psd file with text layers (they are actively installed on my XP system, they appear in the Photoshop type tool's drop-down list).

I close the file. I reopen it three minutes later (because I found a typo).

Upon opening, PS says:

> Some text layers might need to be updated before they can be used for vector based output. Do you want to update these layers now ?

When I click on "Update", the file opens fine, all text layers display properly and can be edited.