Hello!
I came across this problem, then searched the internet and found an unanswered question just like mine:
"When importing word docs, the style mapping no longer works as it did in CS3.
Let's say I mapped the style "text" to "Body Text", I see that all instances of "Body Text" in the indd file have the + indicating local formatting/style override.
I've checked the Word documents and they seem to be styled correctly and indeed, they import just fine into CS3."
http://forums.adobe.com/thread/821695
I must add that same problem also appears when styles are imported automatically (with "conflicts" to solve).
Any comments or suggestions?