InfoJet EditPart needs to store the secondary data in session cache, so it is required to enable the SharePoint session state. Please reference the following articles to enable the suggested SQL Server session state mode:
http://technet.microsoft.com/en-us/library/cc263527.aspx
http://www.sharepointblogs.com/erickraus/archive/2007/12/09/enable-session-state-in-sharepoint-2007.aspx
Or you can enable the InProc session state mode by modifying web.config directly:
1. Uncomment the following line:
    <add name="Session" type="System.Web.SessionState.SessionStateModule" />
2. Modify the following line:
    <pages enableSessionState="true" … />

In WSS 3.0, please open IIS Manager, create a virutal directory named "inlinefiles" in the hosted SharePoint web site, and map it to a disk folder, such as "c:\inlinefiles". Then add the following key into web.config:
<add key="InfoJetSoft.Service.InlineFilePath" value="/inlinefiles" />,
and grant the full control of the folder "c:\inlinefiles" to everyone.

Please add the key such as <add key="InfoJetSoft.Service.TempFolder" value="c:\log" /> to SharePoint's web.config. Then please grant the full control of "c:\log" to everyone. By default, InfoJet Service needs to extract the files in form templates(xsn) to the system temp directory. But in some condition(such as impersonation is enabled in SharePoint), InfoJet Service has no perms to access the folder or files in it, so please add this key.

Please add the key such as <add key="InfoJetSoft.Service.TempFolder" value="c:\log" /> to SharePoint's web.config. Then please grant the full control of "c:\log" to everyone. By default, InfoJet Service needs to extract the files in form templates(xsn) to the system temp directory. But in some condition(such as identity impersonate is enabled in SharePoint), InfoJet Service has no perms to access the folder or files in it, so please add this key.