I used to have a set of rules posted on my wall that I'd point to when some overenthusiastic co-worker want to "fix" something. I've forgotten most of them, but two that I remember:

1. The last thing you touched is what you broke.
2. Never fix anything on a Friday afternoon (in your case this would seem to include the weekend as well).

Remember that some unexplained weird things are caused by hardware problems, and sometimes these may be intermittent. Loose connectors are one of the worst to track down, as are heat related component malfunctions.