So far I don't see any solutions. it's happened to me many times. I have tried many options but so far no proper solutions. ( the below I have used so far )
Solutions 1: Increased memory size to 1GB
parameter : -Xms1024m
locations : C:\Program Files\SmartBear\SoapUI-5.3.0\bin\SoapUI-5.4.0.vmoptions"
Solutions 2: Enabled Autosave after 20 mins and before Autosave create a backup file ( atlist backup copy is not corrupted)
Solutions 3: Disabled autoSave options. and start using Save when I wanted to save
Solutions 4: Disabled and closed unused project in your current workspace.
Solutions 5: If you are running big load ( data-driven test ) where many loops are running, run this project with testRunner batch mode
Solutions 6: If your testSuite is running and you are doing any test Parallel please stop doing this. Many times it got hanged while sending request/response.
with combinations of 3,4,5, I found you will never have faced any issue. but I make mistake and soapUi hanged and Project filled with null null null ( which can't be reverted back )