I found another reason why this happens, On windows 7 the file C:\Users\myuser1\AppData\Roaming\bazaar\2.0\qbzr.conf got somehow corrupted (sympom bzr command line works fine, but from tortoisebzr gives the same error). Fix was to rename the file, relaunch Bazaar explorer and let them create a new one. The complete bzr error I was getting was: bzr: ERROR: bzrlib.util.configobj.configobj.ConfigObjError: Parsing failed with several errors. First error at line 1. Traceback (most recent call last): File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\commands.py", line 176, in run File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\commands.py", line 510, in _qbzr_run File "bzrlib\lazy_import.pyo", line 129, in __call__ File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\log.py", line 113, in __init__ File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\util.py", line 339, in restoreSize File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\util.py", line 128, in get_option File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\util.py", line 109, in _load File "bzrlib\util\configobj\configobj.pyo", line 1223, in __init__ File "bzrlib\util\configobj\configobj.pyo", line 1306, in _load ConfigObjError: Parsing failed with several errors. First error at line 1. bzr 2.4.2 on python 2.6.6 (win32) arguments: ['C:\\Program Files (x86)\\Bazaar\\tbzrcommand.exe', '--command=log', '--file=C:\\src\\MainSource\\features\\DebuggerNewSyncLogic4'] encoding: 'cp1252', fsenc: 'mbcs', lang: 'en' plugins: bzrtools C:\Program Files (x86)\Bazaar\plugins\bzrtools [2.4.1] changelog_merge C:\Program Files (x86)\Bazaar\plugins\changelog_merge [2.4.2] colo C:\Program Files (x86)\Bazaar\plugins\colo [0.3.1dev] explorer C:\Program Files (x86)\Bazaar\plugins\explorer [1.2.1] extmerge C:\Users\fergs\AppData\Roaming\bazaar\2.0\plugins\extmerge [unknown] fastimport C:\Program Files (x86)\Bazaar\plugins\fastimport [0.12.0dev] launchpad C:\Program Files (x86)\Bazaar\plugins\launchpad [2.4.2] loom C:\Program Files (x86)\Bazaar\plugins\loom [2.2.1dev] mysql_plugins C:\Users\fergs\AppData\Roaming\bazaar\2.0\plugins\mysql_plugins [0.4.4] netrc_credential_store C:\Program Files (x86)\Bazaar\plugins\netrc_credential_store [2.4.2] news_merge C:\Program Files (x86)\Bazaar\plugins\news_merge [2.4.2] pipeline C:\Program Files (x86)\Bazaar\plugins\pipeline [1.1.0] qbzr C:\Program Files (x86)\Bazaar\plugins\qbzr [0.21.1] rewrite C:\Program Files (x86)\Bazaar\plugins\rewrite [0.6.3dev] svn C:\Program Files (x86)\Bazaar\plugins\svn [1.1.0] upload C:\Program Files (x86)\Bazaar\plugins\upload [1.0.1dev] xmloutput C:\Program Files (x86)\Bazaar\plugins\xmloutput [0.8.7] The corrupted contents of qbzr.conf are a chunk of .NET Fusion log viewer (how did they output end up there?):
*** Assembly Binder Log Entry  (7/8/2012 @ 12:14:34 AM) ***

The operation failed.
Bind result: hr = 0x80070002. The system cannot find the file specified.

Assembly manager loaded from:  C:\Windows\Microsoft.NET\Framework\v4.0.30319\clr.dll
Running under executable  D:\src\MainSource\Bugs\Bug65065ConstraintExceptionMSSQL\Bug65065ConstraintExceptionMSSQL\bin\Debug\Bug65065ConstraintExceptionMSSQL.vshost.exe
--- A detailed error log follows. 

=== Pre-bind state information ===
LOG: User = 5YJDTM1\fergs
LOG: DisplayName = Microsoft.VisualStudio.HostingProcess.Utilities, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL
 (Fully-specified)
LOG: Appbase = file:///D:/src/xxxx/
LOG: Initial PrivatePath = NULL
LOG: Dynamic Base = NULL
LOG: Cache Base = NULL
LOG: AppName = xxx.vshost.exe
Calling assembly : (Unknown).
===
LOG: Start binding of native image Microsoft.Vis