lets see - I tested this by going into the campains screen, generating a Soviet 1976 LC vs UK USA & CDN, and start buying PT-76 platoons and T-62 coys etc. Repeated a few times, with and without exiting the game.
It allows deletion of the platoons in the formation buy list, and in the main page (where the formation type buttons are shown) quite happily. Message "delete existing core formation Y/N" appears, and if you select Y, the platoon vanishes as expected.
This is on a Dell Dimension 5150, running XP Home.
It may be because your disk needs defragging and/or it has lost clusters and so forth that needs cleaning?.
What year, campaign nation and opponents, and what formations have you bought and tried to delete?. What operating system and PC details?. CD or DL version?. What nationality is the PC set for (on the off chance thet non KeybUK drivers cause problems - you never know with M$
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!)
Cheers
Andy