The code behind Memberium conforms to the strict standards set for WordPress plugin development and is designed to function correctly with other well-written plugins and themes, however conflicts can and do happen.
There are thousands of plugins available for WordPress, with varying goals, qualities of code, and intentions for use.
Some conflicts are intentional, for example there are security plugins which block Infusionsoft’s HTTP POSTs from reaching your site. Examples of this include WP-SpamShield, iThemes Security, etc. The iThemes conflict can be fixed by editing the changes it makes to your .htaccess file, but the WP-Spamshield has no ability to let HTTP POSTs through.
Some conflicts are minor and side effects of the design. If you notice something working oddly or not working after installing another plugin, you can usually narrow it down by disabling the plugins and turning them on one-by-one and testing your site, until you find the plugin causing the problem.