I have an application in C/Motif on Solaris which will go off into some long processing routines which can last several minutes (basically opening large files, reading and manipulating data, then writing out to a new file in a different format). This long processing is started in a Callback function. During this time the GUI main window is essentially locked up. Now, it's not completely locked up because I'm dumping info to a text window and the window is occasionally updated, but the user is not able to access any menus, etc. I assume it's simply because the processing function is eating all the CPU time. Once the Callback process completes the window is accessible again. BTW, I'm running CDE and all other windows outside my application are still active. Is there a solution to this?