I see this problem with "LibreOffice 3.3.0 RC4 - WIN7 Home Premium (64bit) German UI [OOO330m19 (build 6 / tag 18.104.22.168)]". Sometimes ASP "forgets" to underline wrong words, sometimes correct words remain underlined after I have added it to dictionary.
May be you can reproduce the problem with my sample document from test kit; you can see my results in attached "presentation.odp" from test kit:
1. open "sample.odt" with German dictionary available
"Programm" should not be underlined because word is correct
2. duplicate first "r" in "Programm", so that you get "Prrogramm"
3. Move caret to word "Pavillon" using arrow key right
expected: wrong spelled word shoud be underlined
actual: not underlined
4. Press <f7> for spellcheck
Wrong spelled "Prrogramm" will be recognized
Created attachment 43016 [details]
Pls. see original report
Also for me this problem is not 100% reproducible. Most times auto spell check works without problems, sometimes I see incorrect behaviour as described.
No longer reproducible with "LibreOffice 3.3.2RC2 – WIN7 Home Premium (64bit) German UI [OOO330m19 (Build:202 / tag 22.214.171.124)]".
Closing for now