If you click the "Get logs" button in HLSW and it returns an error, you probably have sv_logsecret set to a non-zero value on your server, which changes the format of logfile lines that are streamed to external hosts to a format that HLSW (and any other pre-April-14-2011 utility) does not support.
A new version of your client program may fix this. Alternately, you can work around the problem by setting sv_logsecret back to 0 on your server. If you don't have a configuration file that changes it, check your plugins to see if one of them may be altering it. One other common offender is the 3rd party service gameMe, which enables sv_secret via rcon; if you use it, you can turn that off by disabling the "Secure log" feature in your gameMe account.