This bug is noticeable when vmError is called, which in turn calls logInfo.
In logInfo it tests for the log file and if this file does not exist, logInfo then calls vmError('Could not use path '.$file.' to store log')
A workaround is to ensure that the log file does exist.
This is also connected to topic: http://forum.virtuemart.net/index.php?topic=121112.msg413133#msg413133
VM version: 2.0.26a
Update to 2.0.26d