well.. either there is no proc named xa, or you are executing the timer in the wrong way.. without the code of the timer we can't tell you if that is the case
well i tried to search for something like xa or ya which also appears as an unknown command. but couldn't find them. Well I'll try to search all the scripts even the ones who aren't suspeted...
I noticed in a previous thread, where I replied regarding incorrect list usage.
Are these script by any chance related?
If so, you need to seriously look at the differances between lists and strings, as it looks like you may have a issue in your script, that can pass control to poeple on IRC.
By any chance, does anybody in your channels, have a nickname with [xa] in it?
If so, if they where to change there nickname to say me[die]me, your bot would go pop, and exit.
Have you created any Tcl's yourself, that use timers?
If so, I seriously sugest reading up on string and lists, and using timers, exec and expr with innformation passed from IRC. Links to this documentation, are available in the "Tcl FAQ" forum.