Teresa, can you confirm the version of Phoenix installed and if you also have NONMEM installed on the same machine and if so which version please?
We saw this error at a client who had the G77 compiler for NONMEM already installed to a different directory. Phoenix is hard-coded to look for this in C:\PHSTMinGW.
The workaround that we used at that time was to rename their existing G77 compiler directory (e.g. C:\G77) to C:\G77.bak. Then open Phoenix and see if it can run Phoenix model objects. After they are done using Phoenix, re-name the C:\G77.bak folder back to C:\G77.
Alternatively, this problem may also occur when a textual model is written in PML with a syntax error that is not caught by the DME. If there is no other GNU compiler installed, submit your project if possible to confirm the cause.
Simon.