To isolate which plugin(s) may be contributing to the trouble, deactivate all except WPtouch from within the WordPress Plugins area, clear your browser cache and local data then test.
If WPtouch functions well, you may then enable the rest of your plugins one at a time, repeating the process, until you can identify which is/are causing the problem.
You may choose to replace the conflicting plugin with another or upgrade to WPtouch Pro which has a feature that will allow you to disable the conflicting plugin within your mobile theme but leave your desktop theme intact.
I am using WPTouch free version but I am considering upgrading to PRO but bugs like this one put me off.
WPtouch Pro offers methods to attempt to deactivate plugins within the mobile theme but leave them active in the desktop theme. If you want to give WPtouch Pro a try, there's a 7-day trial period during which you have full access to support and documentation to help you set up your desktop theme's advanced functionality in your mobile theme. You may request a refund at any time within the trial period if you are not happy.