c# - Backload 1.9.3.1 file upload handler generating 500 error out of the blue - nothing changed on server -

we've been using backload in production 2 years without issues. of sudden morning uploads no longer work. there no server/software/config changes , cannot see wrong. checked permissions, disk space etc. no luck. in fact, turned out files being uploaded correctly! failed attempts there in upload directory somehow there failure before upload handler can send json response file info.

fyi, have application on same server (actually demo version of other application - same in every respect except directory files saved (different directory on same drive)) works perfectly.

i enabled tracing try , handle on going wrong, fail - after creating log files , writing first few lines backload component initialization, logging stops. nothing logged uploads.

i don't expect magically solve issue (but if may ask marry me) if has advice on potential problems, helpful. also, if have insights why tracing not working, helpful well. web.config tracing settings follow:

  <system.diagnostics>      <trace autoflush="true">      </trace>      <sources>        <source name="backload" switchname="tracelevel">          <!-- name must "backload".  -->          <listeners>            <!-- trace output can accessed http://[webapp root]/trace.axd -->            <add name="webpagetracelistener" type="system.web.webpagetracelistener, system.web, version=2.0.3600.0, culture=neutral, publickeytoken=b03f5f7f11d50a3a"/>            <add name="logfile" />            <!-- trace output log file, errors (see filter below) -->            <add name="xmlfile" />            <!-- xml output microsoft service trace viewer -->          </listeners>        </source>      </sources>      <sharedlisteners>        <add name="logfile" type="system.diagnostics.textwritertracelistener" initializedata="c:\www\dad.prod\logs\backload.log" traceoutputoptions="datetime">          <!--<filter type="system.diagnostics.eventtypefilter" initializedata="error" />-->          <!--only log errors in listener-->        </add>        <add name="xmlfile" type="system.diagnostics.xmlwritertracelistener" initializedata="c:\www\dad.prod\logs\backload.svclog" traceoutputoptions="datetime" />        <!--traceoutputoptions="datetime,logicaloperationstack,callstack" />-->      </sharedlisteners>      <switches>        <!-- set level @ tracing occur. example: <add name="tracelevel" value="error" /> -->        <!-- valid levels off, critical, warning, information, verbose. optional: activitytracing -->        <!-- turn tracing off set value attribute "off". example: <add name="tracelevel" value="off" /> -->        <add name="tracelevel" value="information, activitytracing, verbose, critical, error" />      </switches>    </system.diagnostics>

thank you

so...i recycled app pool couple times (which loathe because kicks people out of application) , things seem have fixed - uploads work.

i had touched web.config few times (adding tracing settings) thought caused recycle didn't work. when went iis manager , manually recycled app pool did things start work.

thanks