I have a number of worksheets that our students access using MapleNet. They all have embedded plot components, and they all exhibit some variation on the error/issue described at the start of this thread. And it actually is not specific to fieldplot, it happens with all the plot commands. This is in Maple 11 and all worked fine in Maple 10 with Maplenet 10.5. The first time in you get the "invalid plot structure" error. But most of the time if you click the button that draws the plot a second time it works (but not always). The suggestion above, removing "with(plots)" and replacing it with plots:-plot...(...) does also work most of the time, but again, not always. So it seems like there is a larger issue here that needs to be understood. It would be helpful if someone (MapleSoft?) could provide an explanation of what the issue is and how to solve it. I hate to rely on a workaround that "seems to work" for production work. Also, thanks Scott for the workaround, it does work most of the time and allowed me to get up and running. --Kent