The xinitrc-2.9 package contains a new default Xmodmap that has a single assignment---keycode 22 gets assigned Backspace instead of tilde/grave as usual. As a result, our >20 Tektronix terminals suddenly started to do backspace instead of tilde. I do not know if this applies to other kind of terminals. The file was nonexistent as of xinitrc-2.3, but I haven't checked inbetween versions. Note that the default X keyboard works flawlessly with Tektronix terminals. The presence of that Xmodmap file is, at least, debatable.
agreed, we are reverting the inclusion of this file in an xinitrc errata this week.
*** Bug 10603 has been marked as a duplicate of this bug. ***
*** Bug 11355 has been marked as a duplicate of this bug. ***
Looking forward to this fix. In the meantime, after reading /etc/termcap line 477-481, I found out that I temporary can use ^I instead of TAB, which should solve the STILL UNRESOLVED bug in bug report 11355.