Can I safely uninstall "Citrix Tools for Virtual Machines"?
Short answer: no, it is not. From a recent RackSpace KB article possibly outlining the root cause of your problem:
Uninstalling the existing XenServer Tools software will render your server inaccessible.
This is due to the simple fact that the XenServer tools contain paravirtualized drivers (networking, storage) necessary for the virtual system to function correctly. Also:
An earlier version of the XenServer Tools software [...] has been found to cause server instability in rare cases. [...]
If the listed version is less than 6.0-58937 you should upgrade.