SQL2008 bug?

Can this case happen:
From the TASK MANGER show SqlServer is running(status).
but actually the SqlServer is non-responsive.
Cause i click/type ... there is no response at all.

* but other app is running normal.
* that time, sql server is doing nothing. no loader/IIS/query.

from application show runnnig
from performance show normal(not high CPU). is up and down..
from processes: it show normal. like sql is OPEN.

seem like not memory low.
- there is no notice
- and other app is run normal. not feel any slow or what.

finally end task.
- when end task, it say the sql server non-reponsive
- reopen, query no recovery
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suspect:
- virtualbox? the sqlserver(32bit) is stay in virtualbox, win2003(32bit).
the virtualbox is also win2003(32bit)

- OS, when connection(remote) from few place. when disconnection, it cause the active widnows to HANG.
so when reconnect to there... other app work, but the sqlserver remain HANG.(possible need to reconnect from previous place to solve it.