Problem to use a TAGS file

[Germán Arias]

Hi,

I'm experimenting a strange behaviour with a TAGS file. This is loaded with:

;; Add the table for auto-completion.
(setq tags-file-name (expand-file-name "TAGS" gnustep-resources-dir))

But when I try to use it, sometimes I get:

"Error in post-command-hook (completion-in-region--postch): (end-of-buffer)"

Or:

"ESC C-M-i is undefined"

After try 3 or 4 times it works. The TAGS file was generated with etags using 
regex. Any advice? This is with emacs 24.3.1

Germán