from my nintex 2010 wf I call a custom webservice which converts a tiff base64 string to a png and then uploads it to another (!!) webapplication through object model -runwithelevatedprivs. We call this service in a loop about 50 times (different pictures)
Sometimes (not always the same picture) nintex throws time outs on this call, though the picture gets converted and uploaded succesfully.
We increased the nintex time out and indeed it now times out after 4 minutes instead of 2 ;-) So the service is called on 14:00, on 14:00 the picter gets uploaded and on 14:04 nintex times out.