As you know, Oracle in 11g consolidated directories used for all kind of diagnostic operations, for better or worse. Anyway, that includes SQL*Net tracing at client side. On Windows (if not explicitly specified or turned off), trace files will end up deep down under your Documents and Settings folder, for example:

C:\Documents and Settings\alesk\Oracle\oradiag_alesk\diag\clients\user_alesk\host_34047044_11\trace

Fortunately, we can turn this pest off and trace the client the same way as we did before 11g:

sqlnet.ora

DIAG_ADR_ENABLED = OFF
TRACE_LEVEL_CLIENT = 10
TRACE_FILE_CLIENT=11g_odac.trc
TRACE_DIRECTORY_CLIENT=T:\TRACE
...
...