[xcrysden] error for opening Xcrysden (package require BWidget)

[José Xavier]

Dear users, 

I don't know what happened with my xcrysden. Last week it worked fine. This week, it shows me:
Error in startup script: can't find package BWidget
    while executing
"package require BWidget"
    (file "/usr/share/xcrysden/Tcl/xcInit.tcl" line 460)

I remember that this weekend I updated a package of my OS, but I don't know the name...
What could I do to fix this error?