I installed the full version "Simple Image Gallery Pro 2.05"
On localhost XAMP
And it works fine.

But when I brought the site into the air.
I do a new *.zip file upload (in new article) ,And I got an error:

" * UNKNOWNARCHIVETYPE
* Gallery upload error: Cannot extract archive! "


I reinstalled the extension.

I changed permissions to folders: cache, administrator/cache, tmp, media/k2/galleries (777)



*I noticed something : When I upload a file in local server, It create new folder in "media/k2/galleries".
I create the folder by article Id in 'air' server . It delete the folder I created when I do upload.

Try to upload the zip file using a different browser and see what happens.
From K2 support forum

It's the most simple answer that worked, so give it a try for beginning  ;)

Not working! :(

Similar set up:
J! 1.5.19
K2 2.0.3
SIG Pro 2.0.5

Operating System:
Mac – PowerBook G4
Browser: Firefox 3.6.8

Compression of .jpg's using built in, right-click, Mac OS archive utility.

I was banging my thumbs for the past few hours looking for a reason why I could not upload a .zip file using K2 and SIGPRO. I tried all solutions on the forums: changing /administrator/lib/ file solution (found here and on K2 forum), changing /media/k2 folder permissions to 777 (currently set back to 755), unistall/reinstall the SIGPRO plugin, etc. None of these seemed to solve the issue for me as I kept getting the:
* UNKNOWNARCHIVETYPE * Gallery upload error: Cannot extract archive! error.

About 2 weeks ago I recall Firefox automatically upgraded to the newset version. After reading this last suggestion to try another browser, I logged out of admin in Firefox, logged in with another browser (Safari 5.0), clicked on the item created with Firefox and uploaded my .zip file. Success!

Incidently, I had previously noticed that the modified date of an item would be a strange November, 1, 1999. One of those small issues I put to the side to tackle one day. Using Safari cured this problem as well as the item now correctly reflects the modified date/time.

Looks like I will be using Safari to upload items from now on...or at least until the next Firefox update. Hope this helps. 

OK
Bit new at all this

Installed plug in to work with K2.
Only on test site currently
Getting the zip upload error

Tried to change some permissions
Tried chrome, firefox & IE

No joy

Will new module change this?
Is password/test site an issue?
Can I use ftp to get round this?

Cheers
Dom

I'm joining this boat - K2 and SIG 2 Pro don't work together. Nothing shows up in my items

Have you enabled the MooTools upgrade plugin?

MooTools enabled - nothing.

It looks as if it recognizes the gallery b/c Image Gallery (text) and link show up, just no images.

Using Joomla 1.5.20 / SIG Pro 2.0.3 / Php 5.x /

Please provide us with a link to your site.