I don't know what arrow did, but I've had the pluggable combined with wp-db error a coupla times. All I did was make fresh copies of the files, from plain text and saved without BOM, and the problem went away. Deleted the file and uploaded the fresh one immediately to be even more certain than with just overwriting.
I keep 3 sets of backups on disc. An original version. A saved as plain text version. A current with any modifications version.
In this case I checked the db for related active plugin values too (in the wp-options table). If you're comfortable deleting certain values, then they'll be more likely to be re-written properly by clean files. One of the things that's cool about a dynamic db. :)