Help Phone behaving strangely; deleting texts, won't update, browser security exceptions...

[jazbas]

Hi there,

I have a Samsung Galaxy Mini 2 which has been behaving strangely in the last few days. It seemed to start when I dropped it on the floor, although these seem like software problems, so maybe just a coincidence? Anyway, there are at least 3 symptoms which have started up recently, which seem slightly unrelated but all started at the same time:

• When I recieve a text, it vibrates and shows that I have 1 new text. When I open text messaging I can see the message at the top with a preview, but the moment I open it, it's gone - permenantly
• I cannot send any texts. I try, and nothing happens when I press Send.
• I have a notification saying "Set up software update". It prompts me to accept the T&Cs, but if I try, I get "process failed" with no futher explaination
• EVERY website I visit with a secure connection generates a security warning stating that the certificate is not from a trusted source

Can anyone piece together these clues and suggest some cause, or (better!) a fix? Would a factory reset do it? The only vague idea I had is that it could be something to do with the internal storage becoming damaged or corrupt in some way...?

Any ideas much appreciated!

EDIT: I previous said that I had used software update before, but actually it seems this is not the case. (it's my wife's phone...)